Divisiblity problem:

[\'manpreet singh]

Is the sum of integers a and b divisible by 7?

(1) a is not divisible by 7.
(2) a - b is divisible by 7.

[das.ashmita]

Hi Manpreet

The Ans is C

(1) a is not divisible by 7.

for a=15 and b=1 a+b=16 not divisible by 7
for a=15 and b=-1 a+b=14 divisible by 7

not suff

(2) a - b is divisible by 7.

for a=21 and b=7 a-b is divisible by 7 and a+b=14 divisible by 7
for a=15 and b=1 a-b is divisible by 7 but a+b=16 is not divisible by 7

not suff

combining the (1) and (2)

for a=15 and b=1 a-b is divisible by 7 but a+b=16 is not divisible by 7
for a=20 and b=-1 a-b is divisible by 7 but a+b=16 is not divisible by 7

Suff

Hope it helps

[\'manpreet singh]

Thanks Ashmita ,nice explanation!

[theachiever]

1.a is not divisible by 7

This data alone is insufficient since value of b is not known

2.a-b is divisible by 7.

This statement alone is not sufficient

Combining both statements assume values of a and b accordingly.We will get a clear answer without any ambiguity.

Hence Answer is C