Which of the following numbers is divisible by 11?

Question

Philoid · Accepted Answer

Take the alternating sum of the digits in the number, read from left to right. If that is divisible by 11, so is the original number.

A. 1011011

Sum = 1 – 0 + 1 – 1 + 1 – 1 + 1 = 2

Since, 2 is not divisible by 11, 1011011 is not divisible by 11.

B. 1111111

Sum = 1 – 1 + 1 – 1 + 1 – 1 + 1 = 1

Since, 2 is not divisible by 11, 1011011 is not divisible by 11.

C. 22222222

Sum = 2 – 2 + 2 - 2 + 2 – 2 + 2 - 2 = 0

Since, 0 is divisible by 11, 22222222 is divisible by 11.

D. 3333333

Sum = 3 – 3 + 3 – 3 + 3 – 3 + 3 = 3

Since, 3 is not divisible by 11, 3333333 is not divisible by 11.