If a, b and c are even integers greater than 10, is a+b divisible by 6?
All we know is that all the three are multiple of 2.
Thus, a + b can be such that
1a. a and b are equal and each a multiple of 3, leaving us with a YES. E.g. 12 + 12 = 24
1b. Both are a non-multiple of 3, leaving us with with a NO. E.g. 14 + 14 = 28
2a. Both are not equal but sum gives us a multiple of 3, leaving us with a YES. E.g. 14 + 16 = 30
2b. Both are not equal but sum also is a non-multiple of 3, leaving us with a YES. E.g. 16 + 20
and So on..........
So many more possibilities exists.
(1) b=2c
Nothing about c so
1. a = 12 c = 14
b = 28
a + b = 40, NO
2. a = 12, c = 12
b = 24
a + b = 36, YES
INSUFFICIENT.
(2) a=2b
a + b = 2b + b = 3b
Since we already know that b is even i.e. 2x where x is any integer greater than 5,
a + b = 3*2x = 6x
Hence a multiple of 6.
SUFFICIENT.
Answer B.