Chapter 5 of 14

Updated 6 August 2026

NCERT Solutions

A Story of Numbers — NCERT Solutions

Q: What are the important topics in A Story of Numbers for CBSE Class 8 Mathematics?

Key topics in A Story of Numbers include Early Ways of Counting and Representing Numbers, Number Systems Before the Hindu System, The Idea of Base and Place Value, Zero and the Hindu Number System. Study these first, then practise questions on each for Class 8 exams.

Q: Are these NCERT Solutions for A Story of Numbers free?

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Q: How should I revise A Story of Numbers for Class 8 exams?

Learn the core ideas first, then work through the 113 practice questions on A Story of Numbers. Revise definitions regularly and use flashcards for quick recall before the exam.

CBSE · Class 8 · Mathematics

NCERT Solutions for A Story of Numbers, CBSE Class 8 Mathematics: 22 textbook questions solved step by step. Part of the CBSE Class 8 Mathematics syllabus.

113 questions70 flashcards6 formulas & key relations5 concepts

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22 Questions Solved · 9 Sections

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Figure it Out — Section 3.1 (Number Systems using Sticks, Names, and Symbols)

1Suppose you are using the number system that uses sticks to represent numbers, as in Method 1. Without using either the number names or the numerals of the Hindu number system, give a method for adding, subtracting, multiplying and dividing two numbers or two collections of sticks.Show solution

Given: Numbers are represented by collections of sticks (one stick = one unit).

Addition: Place both collections of sticks together into one pile. The resulting collection represents the sum.

Example: ||| + |||| = ||||||| (3 + 4 = 7 sticks)

Subtraction: To subtract a smaller collection B from a larger collection A, pair each stick in B with one stick in A and remove those pairs. The remaining sticks in A represent the difference.

Example: ||||| − ||| → remove 3 pairs → || (5 − 3 = 2 sticks)

Multiplication: To multiply collection A by collection B, make as many copies of collection A as there are sticks in collection B, then combine all copies into one pile.

Example: ||| × || → make 2 copies of ||| → ||| ||| → combine → |||||| (3 × 2 = 6 sticks)

Division: To divide collection A by collection B, repeatedly remove a sub-collection of size equal to B from A and count how many times this can be done. The count (itself represented as a collection of sticks) is the quotient. Any remaining sticks form the remainder.

Example: |||||||| ÷ || → remove || four times → quotient = |||| (8 ÷ 2 = 4)

Thus all four arithmetic operations can be performed purely with physical stick collections, without using Hindu numerals or number names.

2One way of extending the number system in Method 2 is by using strings with more than one letter—for example, we could use 'aa' for 27. How can you extend this system to represent all the numbers? There are many ways of doing it!Show solution

Given: Method 2 uses single letters (e.g., a, b, c, …) for numbers. We extend it using strings of letters.

One possible extension (positional/place-value style):

Assign each letter a value: a = 1, b = 2, c = 3, …, z = 26.

For numbers beyond 26, use two-letter strings where the first letter represents the 'tens-like' position and the second the 'units-like' position. For example, treat it like a base-26 system:

'aa' = 1×26 + 1 = 27
'ab' = 1×26 + 2 = 28
'az' = 1×26 + 26 = 52
'ba' = 2×26 + 1 = 53
'zz' = 26×26 + 26 = 702

For numbers beyond 702, use three-letter strings, and so on. In general, an $n$ -letter string can represent numbers up to $26^n + 26^{n-1} + \cdots + 26$ .

Another possible extension (additive style):

Keep single letters for 1–26, then use repeated letters: 'aa' = 27, 'aaa' = 28, etc. (i.e., each extra 'a' adds 1 beyond 26). This is simpler but less efficient.

Conclusion: There are many valid ways. The key idea is to use combinations of symbols systematically so that every number has a unique representation, which is the foundation of any number system.

3Try making your own number system.Show solution

Sample student-created number system (base-4 using symbols):

Choose four symbols: ✦ (= 0), ● (= 1), ▲ (= 2), ■ (= 3).

Landmark numbers (powers of 4): $4^0=1,\ 4^1=4,\ 4^2=16,\ 4^3=64, \ldots$

Write numbers in positional notation (like base-4):

1 → ●
2 → ▲
3 → ■
4 → ● ✦ (meaning $1\times4 + 0$ )
5 → ● ● (meaning $1\times4 + 1$ )
10 → ▲ ▲ (meaning $2\times4 + 2$ )
16 → ● ✦ ✦ (meaning $1\times16 + 0\times4 + 0$ )

This system uses only 4 symbols, has a base of 4, and can represent every positive integer uniquely. Arithmetic can be performed by carrying when a digit reaches 4 (replace 4 of one symbol with 1 of the next higher position).

Note: Students may create any consistent system. The important features are: a fixed set of symbols, a clear rule for representing each number, and a method for arithmetic.

Figure it Out — Roman Numerals

1Represent the following numbers in the Roman system: (i) 1222 (ii) 2999 (iii) 302 (iv) 715Show solution

Concept: In the Roman system, we express the number as a sum of landmark numbers (I=1, V=5, X=10, L=50, C=100, D=500, M=1000) and write the corresponding symbols.

(i) 1222
$1222 = 1000 + 100 + 100 + 10 + 10 + 1 + 1$
$= M + C + C + X + X + I + I$
$\boxed{MCCXXII}$

(ii) 2999
$2999 = 1000 + 1000 + 500 + 100 + 100 + 100 + 50 + 10 + 10 + 10 + 5 + 1 + 1 + 1$
$= M + M + D + C + C + C + L + X + X + X + V + I + I + I$
$\boxed{MMCCCCLXXXVIII}$

(Note: Some versions of Roman numerals use subtractive notation: 2999 = MMCMXCIX. Both are acceptable; the additive form is used here as per the chapter's approach.)

(iii) 302
$302 = 100 + 100 + 100 + 1 + 1$
$= C + C + C + I + I$
$\boxed{CCCII}$

(iv) 715
$715 = 500 + 100 + 100 + 10 + 5$
$= D + C + C + X + V$
$\boxed{DCCXV}$

Figure it Out — Roman Numerals Addition and Multiplication

(b)Add the following Roman numerals: LXXXVII + LXXVIIIShow solution

Given: LXXXVII + LXXVIII

Step 1: Identify the values.

LXXXVII = 50 + 10 + 10 + 10 + 5 + 1 + 1 = 87
LXXVIII = 50 + 10 + 10 + 5 + 1 + 1 + 1 = 78

Step 2: Combine all symbols.
L, X, X, X, V, I, I + L, X, X, V, I, I, I

Count: L×2, X×5, V×2, I×5

Step 3: Group and simplify (without converting to Hindu numerals).

5 Is = V, so I×5 → V×1 (with 0 Is remaining). Now V count = 2+1 = 3.
2 Vs = X, so V×3 → X×1 + V×1. Now X count = 5+1 = 6.
5 Xs = L, so X×6 → L×1 + X×1. Now L count = 2+1 = 3.
2 Ls = C, so L×3 → C×1 + L×1.

Step 4: Write the result.
C + L + X + V = CLXV

$\text{LXXXVII} + \text{LXXVIII} = \boxed{\text{CLXV}}$

Verification: 87 + 78 = 165 = 100 + 50 + 10 + 5 = CLXV ✓

multiplicationHow will you multiply two numbers given in Roman numerals, without converting them to Hindu numerals? Try to find the product of the following pairs of landmark numbers: V × L, L × D, V × D, VII × IX.Show solution

Method for multiplication in Roman numerals:
Use repeated addition. To multiply A × B, add A to itself B times (or B to itself A times), grouping and simplifying at each step.

V × L (5 × 50):
Add L five times: L + L + L + L + L = 5 Ls.
Since 2 Ls = C, we have: 5 Ls = 2C + L → but 5 Ls = 250.
Actually: 2 Ls = C, so 4 Ls = CC, and 5 Ls = CC + C = CCC...
Let us recount: 2L = C, 4L = CC, 5L = CC + L. But 2C = CC, 5C = D.
So 5L = CCL.
$V \times L = \boxed{CCL} \quad (= 250)$

L × D (50 × 500):
This equals 25,000. In Roman numerals, M = 1000, so 25,000 = 25 × M.
Using an overline to denote ×1000: $\overline{XXV}$ or written as MMMMMMMMMMMMMMMMMMMMMMMM M (25 Ms).
$L \times D = 25{,}000$
(In standard Roman numerals without extensions, this requires 25 M symbols: MMMMM...M (25 times).)

V × D (5 × 500):
Add D five times: D + D + D + D + D = 5 × 500 = 2500.
2D = M, so 4D = MM, 5D = MM + D = MMD.
$V \times D = \boxed{MMD} \quad (= 2500)$

VII × IX (7 × 9):
Add IX (=9) seven times:
$9 \times 7 = 63$
In Roman: 63 = 50 + 10 + 3 = LXIII.
$VII \times IX = \boxed{LXIII} \quad (= 63)$

Observation: Multiplication in Roman numerals is cumbersome because it requires repeated addition and regrouping, which is why Romans used the abacus for such calculations.

Figure it Out — Indigenous Number Systems

1A group of indigenous people in a Pacific island use different sequences of number names to count different objects. Why do you think they do this?Show solution

Answer: Different sequences of number names for different objects likely arose because these communities counted objects that had very different practical significance in their daily lives — for example, counting people, animals, fish, coconuts, or days may each have had cultural, ritual, or practical importance that led to separate counting traditions.

This is similar to how in some languages, different 'classifiers' are used with numbers depending on the shape or type of object being counted (e.g., in Japanese or Chinese). It may also reflect the fact that these communities did not need a single universal number system; instead, each counting context was self-contained and sufficient for its purpose.

In short, the different sequences reflect the cultural and practical contexts in which counting arose, rather than a single abstract notion of number.

2Consider the extension of the Gumulgal number system beyond 6 in the same way of counting by 2s. Come up with ways of performing the different arithmetic operations (+, −, ×, ÷) for numbers occurring in this system, without using Hindu numerals. Use this to evaluate the following:
(i) (ukasar-ukasar-ukasar-ukasar-urapon) + (ukasar-ukasar-ukasar-urapon)
(ii) (ukasar-ukasar-ukasar-ukasar-urapon) – (ukasar-ukasar-ukasar)
(iii) (ukasar-ukasar-ukasar-ukasar-urapon) × (ukasar-ukasar)
(iv) (ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar) ÷ (ukasar-ukasar)Show solution

Background: The Gumulgal system counts by 2s:

urapon = 1
ukasar = 2
ukasar-urapon = 3
ukasar-ukasar = 4
ukasar-ukasar-urapon = 5
ukasar-ukasar-ukasar = 6
ukasar-ukasar-ukasar-urapon = 7
ukasar-ukasar-ukasar-ukasar = 8
ukasar-ukasar-ukasar-ukasar-urapon = 9
ukasar-ukasar-ukasar-ukasar-ukasar = 10

Each 'ukasar' contributes 2, and 'urapon' contributes 1.

Arithmetic methods (without Hindu numerals):

Addition: Combine the two sequences. If the combined sequence has two 'urapon's, replace them with one 'ukasar'. Simplify.
Subtraction: Remove matching terms from the larger sequence. If needed, replace one 'ukasar' with two 'urapon's to facilitate removal.
Multiplication: Repeated addition.
Division: Repeated subtraction, counting how many times the divisor fits.

(i) (ukasar-ukasar-ukasar-ukasar-urapon) + (ukasar-ukasar-ukasar-urapon)

First number = 4 ukasars + 1 urapon = $4 \times 2 + 1 = 9$
Second number = 3 ukasars + 1 urapon = $3 \times 2 + 1 = 7$

Combine: 7 ukasars + 2 urapon. Two urapon = one ukasar, so:
= 8 ukasars + 0 urapon = ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar

$9 + 7 = 16 = \text{ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar}$

(ii) (ukasar-ukasar-ukasar-ukasar-urapon) – (ukasar-ukasar-ukasar)

First = 9, Second = 6.

Remove 3 ukasars from (4 ukasars + 1 urapon):
= 1 ukasar + 1 urapon = ukasar-urapon

$9 - 6 = 3 = \text{ukasar-urapon}$

(iii) (ukasar-ukasar-ukasar-ukasar-urapon) × (ukasar-ukasar)

First = 9, Second = 4.

Add 9 four times:
$9 + 9 = 18$ (ukasar × 9 = ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar)
$18 + 9 = 27$
$27 + 9 = 36$

In Gumulgal notation: $36 = 18 \times \text{ukasar}$ , i.e., 18 ukasars.

$9 \times 4 = 36 = \underbrace{\text{ukasar-ukasar-}\cdots\text{-ukasar}}_{18 \text{ ukasars}}$

(iv) (ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar-ukasar) ÷ (ukasar-ukasar)

First = 8 ukasars = 16, Second = 2 ukasars = 4.

Repeatedly remove groups of (ukasar-ukasar) from (ukasar×8):

Remove once: 6 ukasars remain
Remove twice: 4 ukasars remain
Remove thrice: 2 ukasars remain
Remove four times: 0 remain

Quotient = 4 removals = ukasar-ukasar

$16 \div 4 = 4 = \text{ukasar-ukasar}$

3Identify the features of the Hindu number system that make it efficient when compared to the Roman number system.Show solution

Features of the Hindu number system that make it more efficient than the Roman system:

Place Value (Positional System): In the Hindu system, the value of a digit depends on its position. This means the same digit (e.g., 2) can represent 2, 20, 200, etc., depending on where it is placed. The Roman system has no place value.

Use of Zero (0): The Hindu system has a symbol for zero, which acts as a placeholder and also as a number in its own right. This is absent in the Roman system, making representation of numbers like 100 or 1000 ambiguous without it.

Finite set of symbols: The Hindu system uses only 10 digits (0–9) to represent any number, no matter how large. The Roman system requires new symbols for larger numbers (or cumbersome repetition).

Efficient arithmetic: Addition, subtraction, multiplication, and division are straightforward using the Hindu system's algorithms (column methods). In the Roman system, arithmetic is very difficult and requires tools like the abacus.

Unambiguous representation: Every number has exactly one representation in the Hindu system (ignoring leading zeros). The Roman system can be ambiguous, especially with spacing.

Scalability: The Hindu system can represent arbitrarily large numbers compactly. The Roman system becomes unwieldy for large numbers.

4Using the ideas discussed in this section, try refining the number system you might have made earlier.Show solution

Refinement of the earlier number system (base-4 example):

Earlier system: Used symbols ✦ (0), ● (1), ▲ (2), ■ (3) in a positional base-4 system.

Refinements based on ideas from the chapter:

Ensure zero is a full digit: ✦ (zero) is treated as a number on its own, not just a placeholder. This allows unambiguous representation of numbers like 4 (= ● ✦) and 16 (= ● ✦ ✦).

Positional notation: The position of each symbol determines which power of 4 it represents. Rightmost position = $4^0$ , next = $4^1$ , etc.

Arithmetic rules:

Addition: Add digit by digit from right; carry 1 to the next position whenever a digit reaches 4.
Subtraction: Borrow from the next position when needed (borrowing 1 from the next position gives 4 in the current position).
Multiplication and division: Use standard algorithms adapted for base 4.

Representation of any number: Any positive integer can be uniquely written in this system. For example:

$25 = 1 \times 16 + 2 \times 4 + 1 =$ ● ▲ ● (in base 4: $121_4$ )
$50 = 3 \times 16 + 0 \times 4 + 2 =$ ■ ✦ ▲ (in base 4: $302_4$ )

This refined system is efficient, unambiguous, and supports easy arithmetic — similar to the Hindu system but in base 4.

Figure it Out — Egyptian Number System

1Represent the following numbers in the Egyptian system: 10458, 1023, 2660, 784, 1111, 70707.Show solution

Concept: In the Egyptian system, landmark numbers are powers of 10. Each power of 10 has a unique symbol. A number is written by repeating the symbol for each power of 10 as many times as needed.

Symbols (using descriptions): | = 1, ∩ = 10, 9 = 100, lotus = 1000, finger = 10000, frog = 100000, man = 1000000.

(i) 10458
$10458 = 10000 + 100 + 100 + 100 + 100 + 50 + 5 + 1 + 1 + 1$
Wait, let us decompose properly:
$10458 = 1 \times 10000 + 0 \times 1000 + 4 \times 100 + 5 \times 10 + 8 \times 1$
= 1 finger + 4 lotus-flowers...

Actually using standard Egyptian symbols:
$10458 = 10000 + 400 + 50 + 8$
= 1 (ten-thousand symbol) + 4 (hundred symbols) + 5 (ten symbols) + 8 (unit symbols)

Written as: [finger][9][9][9][9][∩][∩][∩][∩][∩][|][|][|][|][|][|][|][|]

(ii) 1023
$1023 = 1000 + 0 \times 100 + 2 \times 10 + 3 \times 1$
= 1 (thousand symbol) + 2 (ten symbols) + 3 (unit symbols)

Written as: [lotus][∩][∩][|][|][|]

(iii) 2660
$2660 = 2 \times 1000 + 6 \times 100 + 6 \times 10 + 0$
= 2 (thousand symbols) + 6 (hundred symbols) + 6 (ten symbols)

Written as: [lotus][lotus][9][9][9][9][9][9][∩][∩][∩][∩][∩][∩]

(iv) 784
$784 = 7 \times 100 + 8 \times 10 + 4 \times 1$
= 7 (hundred symbols) + 8 (ten symbols) + 4 (unit symbols)

Written as: [9][9][9][9][9][9][9][∩][∩][∩][∩][∩][∩][∩][∩][|][|][|][|]

(v) 1111
$1111 = 1 \times 1000 + 1 \times 100 + 1 \times 10 + 1 \times 1$
= 1 (thousand) + 1 (hundred) + 1 (ten) + 1 (unit)

Written as: [lotus][9][∩][|]

(vi) 70707
$70707 = 7 \times 10000 + 0 \times 1000 + 7 \times 100 + 0 \times 10 + 7 \times 1$
= 7 (ten-thousand symbols) + 7 (hundred symbols) + 7 (unit symbols)

Written as: [finger]×7 [9]×7 [|]×7

2What numbers do these numerals stand for? (i) [Egyptian numeral image i] (ii) [Egyptian numeral image ii]

Note: The actual images of the Egyptian numerals are not visible in the OCR. However, based on the Egyptian system:

Method to decode: Count the number of each type of symbol and multiply by its value:

Each unit symbol (|) = 1
Each ten symbol (∩) = 10
Each hundred symbol (9 or coil) = 100
Each thousand symbol (lotus) = 1000
Each ten-thousand symbol (finger) = 10,000

Then add all values together.

Example: If numeral (i) shows 2 lotus + 3 coils + 4 tens + 5 units:
$= 2000 + 300 + 40 + 5 = 2345$

Students should apply this method to the actual symbols shown in their textbook figures.

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Figure it Out — Base-5 Number System

1Write the following numbers in the above base-5 system using the symbols in Table 2: 15, 50, 137, 293, 651.

Concept: In the base-5 system, landmark numbers are powers of 5: $1, 5, 25, 125, 625, \ldots$

Symbols (from Table 2, as described in the chapter): ✦ or △ = 1, □ = 5, ○ = 25, ◎ = 125, ⊕ = 625 (using placeholder names since the actual table image is not visible).

We express each number in terms of powers of 5:

(i) 15
$15 = 2 \times 5 + 5 = 3 \times 5 + 0 \times 1$
Wait: $15 = 3 \times 5 + 0$
= 3 (five-symbols) + 0 units = □□□

(ii) 50
$50 = 2 \times 25 + 0 \times 5 + 0 \times 1$
= 2 (twenty-five symbols) = ○○

(iii) 137
$137 = 1 \times 125 + 12 \times 1 = 1 \times 125 + 2 \times 5 + 2 \times 1$
Check: $125 + 10 + 2 = 137$ ✓
= 1 (125-symbol) + 2 (5-symbols) + 2 (1-symbols) = ◎□□△△

(iv) 293
$293 = 2 \times 125 + 43 = 2 \times 125 + 1 \times 25 + 18 = 2 \times 125 + 1 \times 25 + 3 \times 5 + 3 \times 1$
Check: $250 + 25 + 15 + 3 = 293$ ✓
= 2 (125-symbols) + 1 (25-symbol) + 3 (5-symbols) + 3 (1-symbols) = ◎◎○□□□△△△

(v) 651
$651 = 1 \times 625 + 26 = 1 \times 625 + 1 \times 25 + 1 \times 1$
Check: $625 + 25 + 1 = 651$ ✓
= 1 (625-symbol) + 1 (25-symbol) + 1 (1-symbol) = ⊕○△

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2Is there a number that cannot be represented in our base-5 system above? Why or why not?

Answer: No, every positive integer can be represented in the base-5 system.

Reasoning:

Any positive integer $N$ can be expressed uniquely as:
$N = a_k \times 5^k + a_{k-1} \times 5^{k-1} + \cdots + a_1 \times 5 + a_0$
where each coefficient $a_i \in \{0, 1, 2, 3, 4\}$ .

This is guaranteed by the Division Algorithm: repeatedly divide $N$ by 5 and record the remainders. The remainders (each between 0 and 4) give the digits of $N$ in base 5.

Since the powers of 5 grow without bound ( $5^0, 5^1, 5^2, \ldots$ ), for any number $N$ , there exists a large enough power $5^k > N$ , and we can always find the representation.

Therefore, every positive integer has a representation in the base-5 system. The system is complete.

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3Compute the landmark numbers of a base-7 system. In general, what are the landmark numbers of a base-

n

system?

Base-7 system:

The landmark numbers are the powers of 7:
$7^0 = 1,\quad 7^1 = 7,\quad 7^2 = 49,\quad 7^3 = 343,\quad 7^4 = 2401,\quad 7^5 = 16807, \ldots$

General base- $n$ system:

The landmark numbers are the powers of $n$ :
$n^0 = 1,\quad n^1 = n,\quad n^2,\quad n^3,\quad n^4, \ldots$

In general, the $k$ -th landmark number (starting from $k = 0$ ) is $n^k$ .

The sequence of landmark numbers is: $1, n, n^2, n^3, n^4, \ldots$

This sequence is infinite, ensuring that every positive integer can be represented in the system.

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Figure it Out — Egyptian and Base-5 Addition

1Add the following Egyptian numerals (as shown in the textbook figures).

Note: The specific Egyptian numeral images are not visible in the OCR. The method for adding Egyptian numerals is as follows:

Method:

Combine all symbols from both numerals.
Count the total of each type of symbol.
Whenever 10 symbols of one type accumulate, replace them with 1 symbol of the next higher type (since each landmark number is 10 times the previous).
Write the simplified result.

Example (from the chapter):
If adding two numbers whose unit symbols total more than 10:

10 unit symbols (|) → replace with 1 ten-symbol (∩)
10 ten-symbols (∩) → replace with 1 hundred-symbol
And so on.

Students should apply this method to the actual numerals shown in their textbook.

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2Add the following numerals that are in the base-5 system: ○○○□△△ + ○○○○□□△△

Given:

First number: ○○○□△△
Second number: ○○○○□□△△

Step 1: Identify values.
Using the base-5 symbols: △ = 1, □ = 5, ○ = 25.

First number: 3 circles + 1 square + 2 triangles = $3 \times 25 + 1 \times 5 + 2 \times 1 = 75 + 5 + 2 = 82$

Second number: 4 circles + 2 squares + 2 triangles = $4 \times 25 + 2 \times 5 + 2 \times 1 = 100 + 10 + 2 = 112$

Step 2: Combine symbols.

Triangles: 2 + 2 = 4 triangles
Squares: 1 + 2 = 3 squares
Circles: 3 + 4 = 7 circles

Step 3: Simplify (5 of one type = 1 of the next).

4 triangles: less than 5, keep as is.
3 squares: less than 5, keep as is.
7 circles: 5 circles = 1 next symbol (125-symbol, let's call it ⊡). So 7 circles = 1 (⊡) + 2 circles.

Step 4: Write result.
= 1 (⊡) + 2 circles + 3 squares + 4 triangles
= ⊡○○□□□△△△△

Verification: $125 + 50 + 15 + 4 = 194 = 82 + 112$ ✓

$\boxed{\text{Result} = \text{⊡○○□□□△△△△} = 194}$

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Figure it Out — Mesopotamian Number System

1Represent the following numbers in the Mesopotamian system: (i) 63 (ii) 132 (iii) 200 (iv) 60 (v) 3605

Concept: The Mesopotamian (Babylonian) system is a base-60 (sexagesimal) positional system. The landmark numbers are powers of 60: $1, 60, 3600, \ldots$

A number is written by expressing it in terms of powers of 60, and writing the coefficient of each power in its respective position (rightmost = units, next = 60s, next = 3600s, etc.).

Symbols: Y = 1, < = 10 (so numbers 1–59 are written using combinations of Y and <).

(i) 63
$63 = 1 \times 60 + 3 \times 1$
Position of 60s: 1 → Y
Position of 1s: 3 → YYY
Mesopotamian numeral: Y | YYY (1 in the 60s place, 3 in the units place)

(ii) 132
$132 = 2 \times 60 + 12 \times 1$
Position of 60s: 2 → YY
Position of 1s: 12 = 10 + 2 → < YY
Mesopotamian numeral: YY | < YY

(iii) 200
$200 = 3 \times 60 + 20 \times 1$
Position of 60s: 3 → YYY
Position of 1s: 20 = 2 × 10 → <<
Mesopotamian numeral: YYY | <<

(iv) 60
$60 = 1 \times 60 + 0 \times 1$
Position of 60s: 1 → Y
Position of 1s: 0 → (blank)
Mesopotamian numeral: Y (with a blank/space indicating the units position is empty)

(This is one of the ambiguities of the Mesopotamian system — 60 looks the same as 1 without a clear zero placeholder.)

(v) 3605
$3605 = 1 \times 3600 + 0 \times 60 + 5 \times 1$
Position of 3600s: 1 → Y
Position of 60s: 0 → (blank)
Position of 1s: 5 → YYYYY
Mesopotamian numeral: Y | (blank) | YYYYY

(Again, the blank for the 60s position illustrates the ambiguity problem of the Mesopotamian system.)

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Figure it Out — Chinese, Binary, and Base Systems

1Why do you think the Chinese alternated between the Zong and Heng symbols? If only the Zong symbols were to be used, how would 41 be represented? Could this numeral be interpreted in any other way if there is no significant space between two successive positions?

Why alternating Zong and Heng symbols:

The Chinese rod numeral system alternated between vertical (Zong) and horizontal (Heng) symbols for successive positions to avoid ambiguity. If the same orientation of symbols were used in adjacent positions, it would be difficult to tell where one position ends and the next begins, especially when there is no clear separator between positions.

For example, three vertical rods in one position and two vertical rods in the next would look like five vertical rods in a single position if written together without spacing. Alternating orientations makes each position visually distinct.

Representation of 41 using only Zong symbols:

$41 = 4 \times 10 + 1$

Using only Zong (vertical) symbols:

Tens position: 4 vertical rods → ||||
Units position: 1 vertical rod → |

Written together: ||||| (5 vertical rods)

Ambiguity: Yes! ||||| could be interpreted as:

41 (4 in tens place, 1 in units place), or
5 (five units), or
50 (5 in tens place, 0 in units place), or
14 (1 in tens place, 4 in units place)

This shows that without alternating symbols or clear spacing, the representation is highly ambiguous. This is precisely why the Chinese system alternated between Zong and Heng symbols.

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2Form a base-2 place value system using 'ukasar' and 'urapon' as the digits. Compare this system with that of the Gumulgal's.

Base-2 (binary) place value system:

Let:

urapon = 0
ukasar = 1

Landmark numbers (powers of 2): $2^0=1,\ 2^1=2,\ 2^2=4,\ 2^3=8,\ 2^4=16, \ldots$

In this positional system, each position represents a power of 2 (from right to left).

Examples:

1 = ukasar (= $1$ )
2 = ukasar-urapon (= $1 \times 2 + 0$ )
3 = ukasar-ukasar (= $1 \times 2 + 1$ )
4 = ukasar-urapon-urapon (= $1 \times 4 + 0 + 0$ )
5 = ukasar-urapon-ukasar (= $1 \times 4 + 0 \times 2 + 1$ )
6 = ukasar-ukasar-urapon (= $1 \times 4 + 1 \times 2 + 0$ )

Comparison with the Gumulgal system:

Feature	Gumulgal System	Base-2 Place Value System
Digits used	urapon (1), ukasar (2) — additive	urapon (0), ukasar (1) — positional
Type	Additive (counting by 2s)	Positional (place value)
Representation of 6	ukasar-ukasar-ukasar	ukasar-ukasar-urapon
Zero	Not present	Present (urapon = 0)
Ambiguity	Possible for large numbers	Unambiguous

The Gumulgal system is an additive system where each 'ukasar' always means 2 and each 'urapon' always means 1, regardless of position. The base-2 place value system uses position to determine the value of each symbol, making it far more efficient and unambiguous.

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3Where in your daily lives, and in which professions, do the Hindu numerals, and 0, play an important role? How might our lives have been different if our number system and 0 hadn't been invented or conceived of?

Role of Hindu numerals and 0 in daily life and professions:

Daily life:

Telling time (clocks, calendars)
Shopping and money transactions
Phone numbers, addresses, PIN codes
Measuring quantities (weight, temperature, distance)
Scoring in sports and games

Professions:

Mathematics and Science: All calculations, equations, and formulas use Hindu numerals.
Engineering and Architecture: Measurements, blueprints, structural calculations.
Medicine: Dosages, patient records, medical statistics.
Banking and Finance: Accounting, interest calculations, stock markets.
Computing and Technology: All digital systems are based on binary (base-2), which is an extension of the place value concept. The digit 0 is fundamental to computing.
Astronomy and Physics: Representing very large and very small numbers (e.g., $6.022 \times 10^{23}$ ).

If the Hindu number system and 0 hadn't been invented:

Arithmetic would be extremely difficult (as seen with Roman numerals).
Advanced mathematics (algebra, calculus) might not have developed.
Modern computers, which rely on binary (0s and 1s), would not exist.
Scientific and technological progress would have been severely limited.
Trade and commerce would be much harder to conduct at scale.
In short, modern civilization as we know it would not have been possible.

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4The ancient Indians likely used base 10 for the Hindu number system because humans have 10 fingers. But what if we had only 8 fingers? How would we be writing numbers then? What would the Hindu numerals look like if we were using base 8 instead? Base 5? Try writing the base-10 Hindu numeral 25 as base-8 and base-5 Hindu numerals, respectively. Can you write it in base-2?

Concept: In a base- $n$ system, we use digits $0, 1, 2, \ldots, n-1$ and each position represents a power of $n$ .

Base-8 (Octal) system:
Digits used: 0, 1, 2, 3, 4, 5, 6, 7 (8 digits, one for each finger if we had 8 fingers).

Base-5 system:
Digits used: 0, 1, 2, 3, 4.

Base-2 (Binary) system:
Digits used: 0, 1.

Converting 25 (base-10) to base-8:
$25 = 3 \times 8 + 1$
So $25_{10} = 31_8$ (digits: 3 and 1)

Verification: $3 \times 8 + 1 = 24 + 1 = 25$ ✓

Converting 25 (base-10) to base-5:
$25 = 1 \times 25 + 0 \times 5 + 0 \times 1 = 1 \times 5^2 + 0 \times 5^1 + 0 \times 5^0$
So $25_{10} = 100_5$

Verification: $1 \times 25 + 0 + 0 = 25$ ✓

Converting 25 (base-10) to base-2:
$25 = 16 + 8 + 1 = 1 \times 2^4 + 1 \times 2^3 + 0 \times 2^2 + 0 \times 2^1 + 1 \times 2^0$
So $25_{10} = 11001_2$

Verification: $16 + 8 + 0 + 0 + 1 = 25$ ✓

Summary:
$25_{10} = 31_8 = 100_5 = 11001_2$

If we had 8 fingers, our number system would naturally be base-8, and we would use only 8 digit symbols. The number 25 would be written as '31' in that system.

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Figure it Out — Section 3.1 (Number Systems using Sticks, Names, and Symbols)

Figure it Out — Roman Numerals

Figure it Out — Roman Numerals Addition and Multiplication

Figure it Out — Indigenous Number Systems

Figure it Out — Egyptian Number System

Figure it Out — Base-5 Number System

Figure it Out — Egyptian and Base-5 Addition

Figure it Out — Mesopotamian Number System

Figure it Out — Chinese, Binary, and Base Systems

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