# Which of the following numbers is not the sum of three consecutive integers: 51, 61, 72, 81?

##### 1 Answer

#### Explanation:

One of the properties of any three consecutive numbers is that their sum is always a multiple of 3.

Why is this?

Consecutive numbers can be written as

The sum of 3 consecutive numbers is given by

=

The

Which of the given numbers are divisible by 3?

You can simply add their digits to find out.

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

Only 61 is not divisible by 3. Therefore it is not the sum of three consecutive numbers.