What is the test of divisibility of 18?

2 Answers
Mar 29, 2016

A number that is divisible by 18 must be divisible by both 2 and 9.

The inverse is also true:
A number that is divisible by both 2 and 9 must be divisible by 18.

Therefore, we just have to test for both divisibility by 2 and 9.

  • If a number is divisible by 2, its last digit must be even.
  • If a number is divisible by 9, the sum of all its digits must be a multiple of 9

If a number passes both tests, then it will surely be divisible by 18.

Mar 29, 2016

Test of divisibility of 18 is that units digit is even i.e. it is either 0,2,4,6 or 8 and simultaneously sum of the digits is divisible by 9.

Explanation:

Factors of 18 are 2 and 9 and hence divisibility by 18 means divisibility both by 2 and 9.

Divisibility test of 2 being that units digit is divisible by 2 i.e. it is either 0,2,4,6 or 8.

Divisibility test of 9 is that sum of all the digits is divisible by 9.

Hence test of divisibility of 18 is that units digit is even i.e. it is either 0,2,4,6 or 8 and simultaneously sum of the digits is divisible by 9.