For a/b>0 both a and b can be positive or both can be negative.
a= +ve, b=+ve OR a=-ve, b-ve
the product a*b will always be +ve, ab>0
Hence C.

tintinusa wrote:If the quotient a/b is positive, which of the following must be true
A. a >0
B. b >0
C. ab >0
D. a-b >0
E. a+b >0

C

I did not understand the logic. Help please!!

quotient a/b is positive. This will happen only when both a and b are of same sign.

Say a = 5, b=2 then quotient = 2 (+ve)
Say a = -8, b=-4 then quotient = 2 (+ve)
Say a = -5, b=2 then quotient = -2 (-ve)

Options:

A. a >0 May be (a=5) Or May not be (a=-8)
B. b >0 May be may not be
C. ab >0 Must be True (as both a and b are of same sign)

So Ans is C

Thanks beat_gmat_09 & shovan85. Got it..you rock!!

tintinusa wrote:If the quotient a/b is positive, which of the following must be true
A. a >0
B. b >0
C. ab >0
D. a-b >0
E. a+b >0

C

I did not understand the logic. Help please!!

Solution:

We are given that a divided by b is positive (or greater than zero). We know that in division when a quotient is positive, the two numbers being divided are either both negative or both positive.

This is also the case in multiplication; that is, to get a product that is positive, we must multiply two positive numbers or two negative numbers. Thus the only answer choice that MUST be positive is ab > 0.

The Answer is C