If b is positive, is ab positive?

Question

(1)  a^2b>0

(2)  a^2+b=13

stonecold · Answer

For ab>0 => a and b must be of the same sign.
So by giving us b>0 the question is really asking us if a>0 or not.

So the question can be transformed into -->
If b>0 then Is a>0 .

Lets begin.

Statement 1-->
a^2 * b > 0

This just tells us that a≠0
a can be positive or negative a^2*b will always be positive.

Hence not sufficient.

Statment 2->
Lets use two examples =>
(0,13)
(1,12)

Hence not sufficient.

Combining the two statements =>

(x,y) => (-1,12) or (1,12) are two easy test cases to take.

Hence not sufficient.

Hence E.

satsurfs · Answer

I would go for E as well. 
1) A^2b > 0 A can be any value and so can B (positive)

2) A^2+B =13 
A^2 can be 12 
B can be 1 
or A^2 (-1^2) can 1 
B can be 12

both 1 and 2 - No difference.

I hope its correct

pushpitkc · Answer

If b is positive, is ab positive?
 
1.  a^2b>0

Since we are given b is positive,
if a is either positive or negative, the expression  a^2b>0  holds true.
Case 1: a=-3, b=2 Here, ab is negative
Case 2: a=3, b=2 Here, ab is positive(Insufficient)
 
2.  a^2+b=13

Since we are given b is positive,
if a is either positive or negative, the expression  a^2+b=13  holds true.
Case 1: a=-3, b=5 Here, ab is negative
Case 2: a=3, b=5 Here, ab is positive(Insufficient)

Even combining both the statements, we will be left with two options
in the first one - both a and b are positive
in the second one - a is negative and b is positive. (Insufficient) (Option E)

sahilvijay · Answer

given b>0
1) (a^2).b>0 from this b>0 then a can be positive as well as negative, so sign of axb can't be determined. A,D ruled out
2) (a^2)+b=13 , b>0 and b <13 a can have Positive and Negative values, also if b>13 , then a is not defined hence sign of axb can't be determined. B ruled out.

Combining both ,
a^2+b = 13 and (a^2) x b > 0 cant solve the problem with the sign from above 2 statements, a can be negative as well as positive since its square will always be positive and therefore C ruled out

Answer is E

SaGa · Answer

+1 E

a^2*b>0 
a can be both positive and negative

a^2 + b = 13 
a can be both positive and negative

Even combining both we do not get if a is positive or negative
Hence E

prerakgoel03 · Answer

St:1 says nothing but what is given in question. B is positive. A can be -ve as well as +ve.Insufficient
St:2 says that a2 will be positive .Again A can be -ve as well as +ve.Insufficient

Combining does not help either.  Therefore E.

AD2GMAT · Answer

Silly Mistake, I did -> assumed that a is positive in place b - marked option D that is incorrect

bumpbot · Answer

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If b is positive, is ab positive?

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If b is positive, is ab positive?

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