Greater common divisior

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IF a and b are positive integers divisible by 6 is b the greatest common divisor of a and b ?

A) a=3b+ 6
B) a=3b

[cramya]

I am getting B)

Stmt II

a=3b

a will have one extra 3 and all the factors of b so b will be gcd of a and and b

SUFF

Stmt I

a= 3b+6
b=6 a = 24

YES

b=12 a=42

NO

INSUFF

Whats the OA?

[muzali]

given: a and b are both divisible by 6

Stm1: a=3b+6
or (a/3)=b+2
because of this "+2" it is insuff to conclude that b is the gcd of (a,b)

Stm2: a=3b
suff because b will be the gcd of (3b,b) i.e., (a,b)

ans:B

[schumi_gmat]

B for me too.

a= 3b
if b = 6, a = 18 and GCD = 6

b= 12, a = 36 and GCD = 12

Hence B