### Mathematics Class VI

Knowing Our Numbers
Whole Numbers
Playing With Numbers
Basic Geometrical Ideas
Fractions
Integers
Decimals
Data Handling
Mensuration
Algebra
Ratio and Proportion
Practical Geometry
Symmetry

# Some More Divisibility Rules

Some More Divisibility Rules

If a number is divisible by another number, then it is also divisible by each of the factors of that number.
For example, 40 is divisible by 20.
Factors of 20 are 1, 2, 4, 5, 10 and 20.
Clearly, 40 is divisible by each of these factors

• If a number is divisible by two co-prime numbers, then it is also divisible by their product.
For example, 40 is divisible by 4 and 5. 4 and 5 are co-prime.
Their product is 4 × 5 = 20.
Clearly, 40 is divisible by 20.
• If two given numbers are divisible by a number, then their sum is also divisible by that number.
For example, the numbers 10 and 25 are divisible by the number 5.
Their sum is 10 + 25 = 35.
Clearly, 35 is divisible by 5.
• If two given numbers are divisible by a number, then their difference is also divisible by that number.
For example, the numbers 10 and 25 are divisible by the number 5.
Their difference is 25 – 10 = 15.
Clearly, 15 is divisible by 5.
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