Question

write a divisibility test of 3 and 9​

Answer 1

If the sum of the digits of a number is divisible by 3, then the number is divisible by 3.

Some examples of numbers divisible by 3 are as follows.

The number 85203 is divisible by 3 because the sum of its digits (8 + 5 + 2 + 0 + 3 = 18) is divisible by 3.

If the sum of the digits of a number is divisible by 9, then the number is divisible by 9.

Some examples of numbers divisible by 9 are as follows.

The number 51984 is divisible by 9 because the sum of its digits (5+ 1 + 9 + 8 + 4 = 27) is divisible by 9.

Answer 2

test of divisibility for 3: sum of the digits must be divisible by 3

test of divisibility for 9: the number must be divisible by 3

Hope that this would help you