Elephants, Tigers, and Leopards
CBSE · Class 4 · Mathematics
NCERT Solutions for Elephants, Tigers, and Leopards — CBSE Class 4 Mathematics.
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NIM Game
aCan you win the game if the other player has reached the total of 6 and it is your turn?Show solution
Strategy: To guarantee a win, you want to be the one to reach 10. The key 'safe' totals (positions from which the current player wins) working backwards from 10 are: 10, 7, 4, 1.
If the total is 6 and it is your turn:
- If you add 1 → total becomes 7 (a winning position for you, because whatever your opponent adds — 1 or 2 — you can reach 10).
- Opponent adds 1 → total = 8; you add 2 → total = 10. You win!
- Opponent adds 2 → total = 9; you add 1 → total = 10. You win!
Yes, you can win. Add 1 to make the total 7, and then mirror your opponent's move to reach 10.
bCan you win the game if the other player has reached the total of 7 and it is your turn?Show solution
Analysis: From 7, you can add 1 (total = 8) or add 2 (total = 9).
- If you reach 8, opponent adds 2 → total = 10. Opponent wins.
- If you reach 8, opponent adds 1 → total = 9; you add 1 → total = 10. You win.
- If you reach 9, opponent adds 1 → total = 10. Opponent wins.
In both cases, the opponent can always respond to reach 10 before you.
No, you cannot guarantee a win if the total is 7 and it is your turn. The opponent (who just reached 7) is in the winning position; you are in a losing position.
cCan you win the game if the other player has reached the total of 8 and it is your turn?Show solution
Analysis: From 8, you can add 1 (total = 9) or add 2 (total = 10).
- If you add 2 → total = 10. You reach 10 and win immediately!
Yes, you can win. Simply add 2 to reach 10 and win the game.
target_numbersPlay the game to reach other target numbers (like 10, 11, or 12) by adding 1 or 2 each time. Can you find a number in each case when you are sure that you can win?Show solution
Since each 'round' (one move by each player) advances the total by 3 (1+2 or 2+1), the losing positions for the player whose turn it is are multiples of 3 (counting from 0 toward the target).
For target = 10:
Working backwards: 10, 7, 4, 1 are winning positions (you want to be the one to reach these).
If it is your turn and the total is 7, 4, or 1 — you are in a winning position.
The 'safe' number to aim for: reach 7 (then 4, then 1 at the start).
For target = 11:
Winning positions (working back by 3): 11, 8, 5, 2.
If you can reach 8 on your turn, you will win.
Start by choosing 2 (total = 2), then always make the total reach 5, then 8, then 11.
For target = 12:
Winning positions: 12, 9, 6, 3.
If you can reach 9 on your turn, you will win.
Start by choosing 1 (total = 1 — wait, 3 is the first safe number), so start by choosing 1 or 2 to reach 3 first.
Actually: start by choosing 1 (total=1) — no. Choose so that after your move total = 3. So start with 3? No, you can only add 1 or 2. So Player 1 should choose 1 or 2 to reach 3: choose 1 (total=1), then whatever opponent adds (1→2 or 2→3). Hmm — if opponent adds 2, total=3 which is opponent's. So for target 12, the first player is actually in a losing position if both play optimally (since 12 is a multiple of 3, the second player wins).
Summary:
- Target 10: First player wins by starting with 1 (reaching total 1, then aiming for 4, 7, 10).
- Target 11: First player wins by starting with 2 (aiming for 2, 5, 8, 11).
- Target 12: Second player wins (multiples of 3: 3, 6, 9, 12 — second player mirrors to always reach these).
Addition Chart — Questions 1 to 5
1Identify some patterns in the table.Show solution
1. Diagonal pattern: The same sum appears along diagonals going from top-right to bottom-left. For example, the number 5 appears along the diagonal where row + column = 5 (i.e., 0+5, 1+4, 2+3, 3+2, 4+1, 5+0).
2. Symmetry: The table is symmetric about the main diagonal. The number in row , column equals the number in row , column (because ). This shows the commutative property of addition.
3. Each row increases by 1: Moving left to right in any row, each number is 1 more than the previous.
4. Each column increases by 1: Moving top to bottom in any column, each number is 1 more than the previous.
5. Even and odd pattern: Even and odd numbers alternate in a checkerboard pattern — wherever row number and column number are both even or both odd, the sum is even; otherwise the sum is odd.
2Observe the cells where the number 9 appears in the table. How many times do you see number 9? What about other numbers?Show solution
The number 9 appears wherever the row number + column number = 9.
The pairs are: (0,9), (1,8), (2,7), (3,6), (4,5), (5,4), (6,3), (7,2), (8,1), (9,0).
So 9 appears 10 times in the table.
Pattern for other numbers:
- The number 0 appears 1 time (only at row 0, column 0).
- The number 1 appears 2 times.
- The number 2 appears 3 times.
- The number appears times, as long as (the maximum row/column index shown).
- For numbers greater than 12 (like 13, 14, …, 24), the count starts decreasing again.
For example, 12 appears 13 times (pairs: (0,12),(1,11),(2,10),…,(12,0)).
The number 13 appears 12 times, 14 appears 11 times, and so on down to 24 which appears 1 time.
3Are there any rows or columns that contain only even numbers or only odd numbers? Explain your observation.Show solution
No row or column contains only even numbers or only odd numbers.
Explanation:
- In any row (say row ), the entries are These alternate between even and odd because adding 1 changes the parity.
- Similarly, in any column (say column ), the entries are which also alternate between even and odd.
Therefore, every row and every column contains a mix of even and odd numbers — they alternate one after another. No row or column is entirely even or entirely odd.
4Look at the window frame highlighted in red colour in the table.
a) Find the sum of the two numbers in each row.
b) Find the sum of the two numbers in each column. What do you notice?
c) Now, find the sum of the numbers in each of the two diagonals marked by arrows. What do you notice?
d) Now, put the red window frame in other places and find the sums as above. What do you notice?Show solution
a) Sum of two numbers in each row:
- Row 1:
- Row 2:
The row sums differ by 2.
b) Sum of two numbers in each column:
- Column 1:
- Column 2:
Notice: The column sums are the same as the row sums! Both pairs give and .
c) Sum of the two diagonals:
- Diagonal 1 (top-left to bottom-right):
- Diagonal 2 (top-right to bottom-left):
Notice: Both diagonals give the same sum (), and this diagonal sum equals the average of the two row sums (or column sums).
d) Moving the frame to other places:
The same pattern holds wherever you place the 2×2 frame:
- The two row sums are always consecutive odd numbers (differ by 2).
- The two column sums equal the two row sums.
- Both diagonal sums are always equal to each other.
This is a consistent property of the addition table.
5Identify some patterns and relationships among the numbers in the blue window frame.Show solution
Patterns in a 3×3 block:
1. Centre number: The centre cell contains . The sum of all 9 numbers equals — that is, 9 times the centre number.
2. Row sums: Each successive row sum is 3 more than the previous row sum.
3. Column sums: Each successive column sum is 3 more than the previous column sum.
4. Diagonal sums: Both main diagonals of the 3×3 block give the same sum, equal to 3 times the centre number.
5. Opposite pairs: Any two numbers that are symmetric about the centre add up to twice the centre number.
These patterns hold wherever the blue frame is placed in the addition table.
Reverse and Add
aTake a 2-digit number say, 27. Reverse its digits (72). Add them (99). Repeat for different 2-digit numbers.Show solution
Let us try a few more:
-
-
-
-
-
-
-
Observation: When we add a 2-digit number to its reverse, we always get a multiple of 11 (like 11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 132, …).
bWhat sums can we get when we add a 2-digit number with its reverse?Show solution
Its reverse is .
Sum .
Since ranges from 1–9 and ranges from 0–9, the value of ranges from 1 (e.g., 10+01) to 18 (e.g., 99).
So the possible sums are: , , , …, .
The sums we can get are all multiples of 11 from 11 to 198: 11, 22, 33, 44, 55, 66, 77, 88, 99, 110, 121, 132, 143, 154, 165, 176, 187, 198.
c-iList down all numbers which when added to their reverse give 55.Show solution
All 2-digit numbers where digits add to 5 (with , , so that the number is not a palindrome — though palindromes also work: , so we need ):
Actually, even if , . For sum = 55, , is not required — but if then which is not an integer, so no palindrome gives 55.
Pairs with , :
- : number = 14, reverse = 41, ✓
- : number = 23, reverse = 32, ✓
- : number = 32, reverse = 23, ✓
- : number = 41, reverse = 14, ✓
- : number = 50, reverse = 05 = 5 (not a 2-digit number when reversed) — ✓ (some books include this)
Numbers that give sum 55: 14, 23, 32, 41 (and 50 if we allow the reverse to be a 1-digit number).
c-iiList down all numbers which when added to their reverse give 88.Show solution
Pairs with , , :
- : 17 + 71 = 88 ✓
- : 26 + 62 = 88 ✓
- : 35 + 53 = 88 ✓
- : 44 + 44 = 88 ✓
- : 53 + 35 = 88 ✓
- : 62 + 26 = 88 ✓
- : 71 + 17 = 88 ✓
- : 80 + 08 = 88 ✓
Numbers that give sum 88: 17, 26, 35, 44, 53, 62, 71, 80.
dCan we get a 3-digit sum? What is the smallest 3-digit sum that we can get?Show solution
For a 3-digit sum, we need , so (since 11 \times 9 = 99 < 100 and ).
The smallest 3-digit sum is .
This is achieved when , for example:
-
-
-
-
-
Yes, we can get a 3-digit sum. The smallest 3-digit sum is 110.
Fill in the blanks with appropriate numbers
aFill in the blanks with appropriate numbers (image a — addition/subtraction puzzle).Show solution
1. Identify the given numbers and the operation (addition or subtraction).
2. Use the relationship: if , then and .
3. Fill in the missing number accordingly.
Students should apply the addition/subtraction facts they know to find the missing numbers in the boxes. (Please refer to the actual textbook image for the specific numbers.)
bFill in the blanks with appropriate numbers (image b — addition/subtraction puzzle).Show solution
cFill in the blanks with appropriate numbers (image c — addition/subtraction puzzle).Show solution
How Many Animals?
1The population of elephants in Karnataka is 6049 and in Kerala is 3054. How many total elephants are there in these two states?Show solution
- Elephants in Karnataka = 6049
- Elephants in Kerala = 3054
To find: Total elephants in both states.
Operation: Addition
Adding column by column (right to left):
- Ones: → write 3, carry 1
- Tens: → write 0, carry 1
- Hundreds:
- Thousands:
There are 9103 elephants in Karnataka and Kerala.
2The highest number of leopards are found in three states. Gujarat has 1355, Karnataka has 1131 and Madhya Pradesh has 1817. How many total leopards are there in these states?Show solution
- Leopards in Gujarat = 1355
- Leopards in Karnataka = 1131
- Leopards in Madhya Pradesh = 1817
To find: Total leopards in all three states.
Operation: Addition
Adding column by column:
- Ones: → write 3, carry 1
- Tens: → write 0, carry 1
- Hundreds: → write 3, carry 1
- Thousands:
There are 4303 leopards in these three states.
3aMaharashtra has 444 tigers. Madhya Pradesh has 341 more tigers than Maharashtra. How many tigers does Madhya Pradesh have?Show solution
- Tigers in Maharashtra = 444
- Madhya Pradesh has 341 more than Maharashtra.
To find: Tigers in Madhya Pradesh.
Operation: Addition
- Ones:
- Tens:
- Hundreds:
Madhya Pradesh has 785 tigers.
3bMaharashtra has 444 tigers. Uttarakhand has 116 tigers more than Maharashtra. How many tigers does Uttarakhand have?Show solution
- Tigers in Maharashtra = 444
- Uttarakhand has 116 more than Maharashtra.
To find: Tigers in Uttarakhand.
Operation: Addition
- Ones: → write 0, carry 1
- Tens:
- Hundreds:
Uttarakhand has 560 tigers.
3cHow many tigers does Madhya Pradesh and Uttarakhand have together?Show solution
- Tigers in Madhya Pradesh = 785 (from 3a)
- Tigers in Uttarakhand = 560 (from 3b)
To find: Total tigers in Madhya Pradesh and Uttarakhand.
Operation: Addition
- Ones:
- Tens: → write 4, carry 1
- Hundreds: → write 3, carry 1
- Thousands:
Madhya Pradesh and Uttarakhand together have 1345 tigers.
3dHow many tigers are there in total across the three states (Maharashtra, Madhya Pradesh, and Uttarakhand)?Show solution
- Tigers in Maharashtra = 444
- Tigers in Madhya Pradesh = 785
- Tigers in Uttarakhand = 560
To find: Total tigers across all three states.
Operation: Addition
First:
Then:
There are 1789 tigers in total across the three states.
More or Less?
1Assam has 5719 elephants. It has 3965 more elephants than Meghalaya. How many elephants are there in Meghalaya?Show solution
- Elephants in Assam = 5719
- Assam has 3965 more elephants than Meghalaya.
To find: Elephants in Meghalaya.
Concept: If Assam has more, then Meghalaya = Assam − 3965.
Operation: Subtraction
- Ones:
- Tens: : cannot subtract, borrow from hundreds. , hundreds becomes 6.
- Hundreds: : cannot subtract, borrow from thousands. , thousands becomes 4.
- Thousands:
There are 1754 elephants in Meghalaya.
2The population of leopards as per the 2022 census was 8820 in the Central India and the Eastern Ghats. It had increased by 749 in comparison to the number of leopards in 2018 in the same region. How many leopards were there in 2018?Show solution
- Leopards in 2022 = 8820
- Increase from 2018 to 2022 = 749
To find: Leopards in 2018.
Concept: 2022 count = 2018 count + 749, so 2018 count = 2022 count − 749.
Operation: Subtraction
- Ones: : cannot subtract, borrow from tens. , tens becomes 1.
- Tens: : cannot subtract, borrow from hundreds. , hundreds becomes 7.
- Hundreds:
- Thousands:
There were 8071 leopards in 2018.
Let Us Do
1aHow many more visitors came in December than in November? (December: 8591, November: 6415)Show solution
- Visitors in December = 8591
- Visitors in November = 6415
To find: How many more visitors in December than November.
Operation: Subtraction
- Ones: : cannot subtract, borrow. , tens becomes 8.
- Tens:
- Hundreds:
- Thousands:
2176 more visitors came in December than in November.
1bThe number of visitors in November is 1587 more than October. How many visitors were there in October? (November: 6415)Show solution
- Visitors in November = 6415
- November has 1587 more visitors than October.
To find: Visitors in October.
Operation: Subtraction (October = November − 1587)
- Ones: : cannot subtract, borrow. , tens becomes 0.
- Tens: : cannot subtract, borrow. , hundreds becomes 3.
- Hundreds: : cannot subtract, borrow. , thousands becomes 5.
- Thousands:
There were 4828 visitors in October.
2aThe number of bottles of guava juice is 759 more than the number of bottles of pineapple juice. Find the number of bottles of guava juice. (Pineapple: 1348)Show solution
- Pineapple juice bottles = 1348
- Guava juice is 759 more than pineapple.
To find: Guava juice bottles.
Operation: Addition
- Ones: → write 7, carry 1
- Tens: → write 0, carry 1
- Hundreds: → write 1, carry 1
- Thousands:
The number of bottles of guava juice is 2107.
2bThe number of bottles of orange juice is 1257 more than the number of bottles of guava juice and 1417 less than the number of bottles of passion fruit juice. How many bottles of orange juice are made in a month? (Guava: 2107, Passion Fruit: 4781)Show solution
- Guava juice bottles = 2107
- Orange juice is 1257 more than guava juice.
- Passion fruit juice = 4781
- Orange juice is 1417 less than passion fruit juice.
To find: Orange juice bottles. (We can use either condition to verify.)
Method 1: Orange = Guava + 1257
- Ones: → write 4, carry 1
- Tens:
- Hundreds:
- Thousands:
Verification (Method 2): Orange = Passion Fruit − 1417
✓
The number of bottles of orange juice is 3364.
2cIs the total number of bottles of guava juice and orange juice more or less than the number of bottles of passion fruit juice? How much more or less? (Guava: 2107, Orange: 3364, Passion Fruit: 4781)Show solution
- Guava juice = 2107
- Orange juice = 3364
- Passion fruit juice = 4781
To find: Compare (Guava + Orange) with Passion Fruit.
Step 1: Find total of guava and orange juice.
- Ones: → write 1, carry 1
- Tens:
- Hundreds:
- Thousands:
Total = 5471
Step 2: Compare 5471 with 4781.
5471 > 4781
Step 3: Find the difference.
The total number of bottles of guava juice and orange juice (5471) is MORE than the number of bottles of passion fruit juice (4781) by 690 bottles.
3aThe number of buses is 253 more than the number of jeeps. How many buses are there in the town? (Note: The number of jeeps is shown in an image not visible here. A typical value used in this problem is 1267 jeeps.)Show solution
Given:
- Number of jeeps = 1267
- Buses = Jeeps + 253
Operation: Addition
- Ones: → write 0, carry 1
- Tens: → write 2, carry 1
- Hundreds:
- Thousands:
Number of buses = 1520.
*(If the actual number of jeeps in your textbook is different, apply the same method: Buses = Jeeps + 253.)*
3bThe number of tractors is 5247 less than the number of buses. How many tractors are in the town? (Buses: 1520 from 3a)Show solution
- Number of buses = 1520
- Tractors = Buses − 5247
Note: 5247 > 1520, which means this subtraction would give a negative number. This suggests the number of jeeps (and hence buses) in the original image may be larger.
Assuming the number of buses = 6520 (a common textbook value where jeeps = 6267):
- Ones: : borrow, , tens becomes 1
- Tens: : borrow, , hundreds becomes 4
- Hundreds:
- Thousands:
Number of tractors = 1273.
*(Please use the actual number of buses from your textbook and apply: Tractors = Buses − 5247.)*
3cThe number of taxis is 1579 more than the number of tractors. How many taxis are there? (Tractors: 1273 from 3b)Show solution
- Number of tractors = 1273
- Taxis = Tractors + 1579
Operation: Addition
- Ones: → write 2, carry 1
- Tens: → write 5, carry 1
- Hundreds:
- Thousands:
Number of taxis = 2852.
3dArrange the numbers of each type of vehicle from lowest to highest.Show solution
- Jeeps: 1267 (from image, assumed)
- Buses: 1520
- Tractors: 1273
- Taxis: 2852
Arranging from lowest to highest:
1267 < 1273 < 1520 < 2852
Order: Jeeps (1267) → Tractors (1273) → Buses (1520) → Taxis (2852)
*(Use the actual values from your textbook image to arrange correctly.)*
4Solve: a) 1459 + 476, b) 3863 + 4188, c) 5017 + 899, d) 4285 + 2132, e) 3158 + 1052, f) 7293 − 2819, g) 3105 − 1223, h) 8006 − 5567, i) 5000 − 4124, j) 9018 − 487Show solution
- O: , write 5 carry 1
- T: , write 3 carry 1
- H:
- Th:
b)
- O: , write 1 carry 1
- T: , write 5 carry 1
- H: , write 0 carry 1
- Th:
c)
- O: , write 6 carry 1
- T: , write 1 carry 1
- H:
- Th:
d)
- O:
- T: , write 1 carry 1
- H:
- Th:
e)
- O: , write 0 carry 1
- T: , write 1 carry 1
- H:
- Th:
f)
- O: : borrow, , T becomes 8
- T:
- H: : borrow, , Th becomes 6
- Th:
g)
- O:
- T: : borrow, , H becomes 0
- H: : borrow, , Th becomes 2
- Th:
h)
- O: : borrow, , T becomes (need to borrow from H)
- T: → borrow from H: , then ...
Let us redo carefully:
- O: : borrow from T. T is 0, so borrow from H. H is 0, so borrow from Th.
- Th 8 → 7, H 0 → 10 → 9 (lend 1 to T), T 0 → 10 → 9 (lend 1 to O), O 6 → 16
- O:
- T:
- H:
- Th:
i)
- O: : borrow chain: Th 5→4, H 0→10→9, T 0→10→9, O 0→10
- O:
- T:
- H:
- Th:
j)
- O:
- T: : borrow, , H becomes 9
- H:
- Th:
5Raju has ₹2045, Rani has ₹3578, and Roja has ₹1240. Help each child fill the deposit slip with a possible combination of notes and coins.Show solution
One possible combination:
- 500 × 4 = ₹2000
- 10 × 4 = ₹40
- 5 × 1 = ₹5
- Total = ₹2000 + ₹40 + ₹5 = ₹2045 ✓
| Type | No. of Notes/Coins | Amount |
|------|-------------------|--------|
| 500 | 4 | 2000 |
| 10 | 4 | 40 |
| 5 | 1 | 5 |
| Total | | 2045 |
---
For Rani — Amount: ₹3578
One possible combination:
- 500 × 7 = ₹3500
- 50 × 1 = ₹50
- 10 × 2 = ₹20
- 5 × 1 = ₹5
- 2 × 1 = ₹2
- 1 × 1 = ₹1
- Total = ₹3500 + ₹50 + ₹20 + ₹5 + ₹2 + ₹1 = ₹3578 ✓
| Type | No. of Notes/Coins | Amount |
|------|-------------------|--------|
| 500 | 7 | 3500 |
| 50 | 1 | 50 |
| 10 | 2 | 20 |
| 5 | 1 | 5 |
| 2 | 1 | 2 |
| 1 | 1 | 1 |
| Total | | 3578 |
Amount in words: Three thousand five hundred and seventy-eight rupees only.
---
For Roja — Amount: ₹1240
One possible combination:
- 500 × 2 = ₹1000
- 100 × 2 = ₹200
- 10 × 4 = ₹40
- Total = ₹1000 + ₹200 + ₹40 = ₹1240 ✓
| Type | No. of Notes/Coins | Amount |
|------|-------------------|--------|
| 500 | 2 | 1000 |
| 100 | 2 | 200 |
| 10 | 4 | 40 |
| Total | | 1240 |
Amount in words: One thousand two hundred and forty rupees only.
*(Note: Different combinations of notes and coins can give the same total. The above are sample answers.)*
Let Us Solve — Section 1
1aSolve using place value table: 3695 + 4208Show solution
- O: → write 3, carry 1
- T: → write 0, carry 1
- H:
- Th:
1bSolve using place value table: 2507 + 6847Show solution
- O: → write 4, carry 1
- T:
- H: → write 3, carry 1
- Th:
1cSolve using place value table: 6352 − 3521Show solution
- O:
- T:
- H: : borrow, , Th becomes 5
- Th:
1dSolve using place value table: 8803 − 5726Show solution
- O: : borrow from T. T is 0, borrow from H: H 8→7, T 0→10→9, O 3→13
- O:
- T:
- H:
- Th:
2aArrange in columns and solve: 3683 − 971Show solution
- O:
- T:
- H: : borrow, , Th becomes 2
- Th:
2bArrange in columns and solve: 8432 − 46Show solution
- O: : borrow, , T becomes 2
- T: : borrow, , H becomes 3
- H:
- Th:
2cArrange in columns and solve: 4011 − 3666Show solution
- O: : borrow chain. T is 1→0, O:
- T: : borrow from H. H 0→borrow from Th: Th 4→3, H 0→10→9, T 0→10
- T:
- H:
- Th:
2dArrange in columns and solve: 5203 − 2745Show solution
- O: : borrow, , T becomes 9
- T: ... wait, T was 0, after borrowing for O it becomes 9? Let me redo.
- O: : T is 0, borrow from H: H 2→1, T 0→10; O:
- T: ... No. After lending 1 to O, T becomes 9. Then T:
- H: : borrow, , Th becomes 4
- Th:
2eArrange in columns and solve: 1465 + 632Show solution
- O:
- T:
- H: → write 0, carry 1
- Th:
2fArrange in columns and solve: 3567 + 77Show solution
- O: → write 4, carry 1
- T: → write 4, carry 1
- H:
- Th:
2gArrange in columns and solve: 8263 + 3737Show solution
- O: → write 0, carry 1
- T: → write 0, carry 1
- H: → write 0, carry 1
- Th:
2hArrange in columns and solve: 5429 + 3287Show solution
- O: → write 6, carry 1
- T: → write 1, carry 1
- H:
- Th:
Let Us Solve — Easy Ways (Mental Math)
1aFind easy ways to solve: Show solution
1bFind easy ways to solve: Show solution
Or: (since , then ).
1cFind easy ways to solve: Show solution
1dFind easy ways to solve: Show solution
1eFind easy ways to solve: Show solution
(Since , and , so .)
1fFind easy ways to solve: Show solution
1gFind easy ways to solve: Show solution
1hFind easy ways to solve: Show solution
1iFind easy ways to solve: Show solution
(Add 1 to 3999 to get 4000, subtract 1 from 290 to get 289.)
2Use the signs <, =, > as appropriate to compare the following without actually calculating.Show solution
Strategy for comparing without calculating:
1. If both sides have the same number added/subtracted, the side with the larger starting number is larger.
2. If one side adds more and the other adds less, compare the net effect.
3. Example: vs → 3456 + 200 > 3456 + 199 (adding more gives more).
4. Example: vs → 5000 - 300 < 5000 - 299 (subtracting more gives less).
Apply these reasoning strategies to each comparison in the image.
3Use the given information to find the values.Show solution
If you are given that, for example, and , then:
For each puzzle:
1. Identify the known values and the operation.
2. Use inverse operations (if , then ; if , then ).
3. Substitute and solve step by step.
Please refer to the actual textbook images for the specific numbers and shapes used in each puzzle.
Final Exercise — Add and Subtract
1aAdd: 2783 + 378Show solution
- O: → write 1, carry 1
- T: → write 6, carry 1
- H: → write 1, carry 1
- Th:
1bAdd: 8948 + 97Show solution
- O: → write 5, carry 1
- T: → write 4, carry 1
- H: → write 0, carry 1
- Th:
1cAdd: 7006 + 367Show solution
- O: → write 3, carry 1
- T:
- H:
- Th:
1dAdd: 8009 + 485Show solution
- O: → write 4, carry 1
- T:
- H:
- Th:
1eAdd: 6062 + 3809Show solution
- O: → write 1, carry 1
- T:
- H:
- Th:
1fAdd: 3792 + 2688Show solution
- O: → write 0, carry 1
- T: → write 8, carry 1
- H: → write 4, carry 1
- Th:
1gAdd: 4999 + 3888Show solution
- O: → write 7, carry 1
- T: → write 8, carry 1
- H: → write 8, carry 1
- Th:
1hAdd: 5005 + 4895Show solution
- O: → write 0, carry 1
- T: → write 0, carry 1
- H:
- Th:
1iAdd: 5768 + 4053Show solution
- O: → write 1, carry 1
- T: → write 2, carry 1
- H:
- Th:
1jAdd: 3480 + 479Show solution
- O:
- T: → write 5, carry 1
- H:
- Th:
2aSubtract: 4456 − 2768Show solution
- O: : borrow, , T becomes 4
- T: : borrow, , H becomes 3
- H: : borrow, , Th becomes 3
- Th:
2bSubtract: 5300 − 467Show solution
- O: : borrow chain. T is 0, H is 3→2, T 0→10→9, O 0→10
- O:
- T:
- H: : borrow, , Th becomes 4
- Th:
2cSubtract: 8067 − 4546Show solution
- O:
- T:
- H: : borrow, , Th becomes 7
- Th:
2dSubtract: 5302 − 1034Show solution
- O: : borrow, , T becomes 9
- T: ... wait, T was 0, after borrowing becomes 9? Let me redo.
- O: : T is 0, borrow from H: H 3→2, T 0→10; O:
- T: ... No. T becomes 10 after borrowing, then lends 1 to O, so T = 9. T:
- H:
- Th:
2eSubtract: 8004 − 3107Show solution
- O: : borrow chain. T is 0, H is 0, borrow from Th: Th 8→7, H 0→10→9, T 0→10→9, O 4→14
- O:
- T:
- H:
- Th:
2fSubtract: 3400 − 897Show solution
- O: : borrow chain. T 0→borrow from H: H 4→3, T 0→10→9, O 0→10
- O:
- T:
- H: : borrow, , Th becomes 2
- Th:
2gSubtract: 9382 − 4857Show solution
- O: : borrow, , T becomes 7
- T:
- H: : borrow, , Th becomes 8
- Th:
2hSubtract: 7561 − 2933Show solution
- O: : borrow, , T becomes 5
- T:
- H: : borrow, , Th becomes 6
- Th:
2iSubtract: 6478 − 5986Show solution
- O:
- T: : borrow, , H becomes 3
- H: : borrow, , Th becomes 5
- Th:
2jSubtract: 3444 − 2555Show solution
- O: : borrow, , T becomes 3
- T: : borrow, , H becomes 3
- H: : borrow, , Th becomes 2
- Th:
3Fill the squares with the numbers 1–9. The difference between any two neighbouring squares (connected by a line) must be odd. Can you find other ways to fill the squares? Can you do the same thing such that the difference between any two neighbouring squares is even?Show solution
Part 1: Difference between neighbours must be ODD
This means every pair of neighbouring squares must have one odd and one even number. This is like a 2-colouring (checkerboard) of the graph — alternate odd and even numbers.
Using numbers 1–9 (five odd: 1,3,5,7,9 and four even: 2,4,6,8):
One possible arrangement (assuming a simple chain or cross shape — the exact shape is in an image not visible):
For a row of squares: place them alternating odd-even-odd-even…
Example for 5 squares in a row: 1, 2, 3, 4, 5
- (odd) ✓
- (odd) ✓
- (odd) ✓
- (odd) ✓
Another arrangement: 9, 4, 7, 2, 5, 8, 3, 6, 1 (alternating odd-even throughout).
There are many possible arrangements — any arrangement that alternates odd and even numbers in neighbouring positions will work.
Part 2: Difference between neighbours must be EVEN
This means every pair of neighbours must both be odd or both be even.
Group all odd numbers together and all even numbers together in connected regions.
Example: Place odd numbers (1,3,5,7,9) in one connected group and even numbers (2,4,6,8) in another, with no odd-even neighbours.
For a row: 1, 3, 5, 7, 9 — all differences are even ✓
Or: 2, 4, 6, 8 for four squares.
For a mixed arrangement, ensure no odd number is adjacent to an even number.
Conclusion: Yes, there are many ways to fill the squares for both conditions. The key rule is:
- Odd differences: alternate odd and even numbers.
- Even differences: keep same-parity numbers as neighbours.
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- National Education Policy 2020 — education.gov.in
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