Playing With Numbers
ICSE · Class 8 · Mathematics
Summary of Playing With Numbers for ICSE Class 8 Mathematics. Key concepts, important points, and chapter overview.
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Overview
Numbers can be written in generalized form using place values, and special patterns help in solving number puzzles quickly. Two-digit and three-digit numbers can be split into digit-based expressions such as ab = 10a + b and abc = 100a + 10b + c. These forms make it easier to study reversals, cyclic
Key Concepts
A number is written as
A number is written as the sum of the products of its digits and their place values. For example, 3479 = 3 × 1000 + 4 × 100 + 7 × 10 + 9 × 1.
A two
A two-digit number with tens digit a and units digit b is written as ab = 10a + b. Here, a is from 1 to 9 and b is from 0 to 9. Also, ab does not mean
A three
A three-digit number with digits a, b, and c is written as abc = 100a + 10b + c. The numbers bca and cab are formed by cyclic change of digits.
For a two
For a two-digit number ab and its reverse ba, ab + ba = 11(a + b). So the sum is divisible by 11 and by the sum of the digits.
For a two
For a two-digit number ab and its reverse ba, ab - ba = 9(a - b) and ba - ab = 9(b - a). So the difference is divisible by 9 and by the difference of
Learning Objectives
- Write numbers in generalized form using place values.
- Express two-digit and three-digit numbers in algebraic form.
- Use properties of reversed digits and cyclic digit changes.
- Apply divisibility tests for 2, 3, 4, 5, 6, 7, 9, 10, and 11.
- Solve simple cryptarithms by finding digit values from place-value clues.
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