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
OA: C
Thanks,
1) a is not divisible by 7
2) a-b is divisible by 7
OA: C
Thanks,
Let a = 2, b=5gvosough wrote: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
OA: C
Thanks,
2 not div by 7
but 2+5 = 7 is div by 7.... YES
let a= 2, b=3
a is not div by 7
but sum = 4 is not div by 7.. NO
INSUFF
a-b is divisible by 7
Let a=2. b=2
a-b = 0 is div by 7
2+2 = 4 is not div by 7... NO
let a=7,b=0
a-b=7 is div by 7
sum = 7 is div by 7.. YES
INSUFF
combining:
a-b is div by 7
so a-b = 7k
a=7k+b
a is not div by 7
hence b cannot be a multiple of 7
if b is not a multiple of 7, then 2b is also not a multiple of 7
a+b = 7k+2b
hence a+B cannot be a multiple of 7.
Answer is always NO
SUFF
pick C
