Discussion Forum



1)

How many of the following numbers are divisible by 3 but not by 9 ?

2133, 2343, 3474, 4131, 5286, 5340, 6336, 7347, 8115, 9276


A) 5

B) 6

C) 7

D) None of these

Answer:

Option B

Explanation:

Marking (-) those which are are divisible by 3 by not by 9 and the others by (X), by taking the sum of digits, we get

2+1+3+3 = 9 (X)
2+3+4+3 = 12 (-)
3+4+7+4 = 18 (X)
4+1+3+1 = 9 (X)
5+2+8+6 = 21 (-)
5+3+4+0 = 12 (-)
6+3+3+6 = 18 (X)
7+3+4+7 = 21 (-)
8+1+1+5 = 15 (-)
9+2+7+6 = 24 (-)
Required number of numbers = 6.