x97agarwal wrote:

young_gun wrote:

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

(1) a = 2b + 6

(2) a = 3b

S1. take b = 6, 12, 18 and any multiple of six

You will always get that six is the greatest common divisor

42 = 2(18) +6 so here six is the greatest common divisor

S2. 36 = 3(12)

here the greatest common 12 divisor is 12. Whatever the value of B is that is the greatest common divisor.

IMO A

a and b are divisible by 6

hence

(1) a=2b+6 => say b=6k k is any integer =>

a=2(6k)+6 => a=(2k+1)6

again to get the greatest common factor other than 6 here

k =2k+1=> k=-1

hence a=-6 a,b are posiive hence this is ruled out SUFFI 6 is greatest common divisor

(2)a=3b =>say b=6k a=18k k can be anything hence greatest common divisor can be any integer other than 6 too INSUFFI

IMO A

_________________

cheers

Its Now Or Never