Question

If 418 - 1 = 687194a6735, then the value of a is
(1) 6 (2) 3 (3) 7
(4) 5
(Andhra Pradesh, Stage-1, 2015-16)​

Answer 1

Answer:

The last five digits must be divisible by 32.

That is, a6736 must be divisible by 32.

This is only possible for a=1,3,5,7,9.

The last 6 digits must be divisible by 64.

Only a=3,7 pass this test.

The last 7 digits must be divisible by 128.

Only a= 7 passes this test.

Hence, the value of a is 7.