The volume of cylinder A is how much more than the volume of cylinder

Question

The volume of cylinder A is how much more than the volume of cylinder B if cylinder A has x+4 radius and cylinder B has a height of 4?

1) cylinder B has a volume of 6
2) the ratio of cylinder A's volume to cylinder B's volume is 4:7

riskietech · Answer

First of all the question is the diff betwn volume of A & B. From st 2 we cannot find this. In fact, looking at the ratio, vol of B is more than A. If quest would have been "what percentage more" then "Personal Answer" would have been "B".

eshan429 · Answer

Would anyone mind explaining how B alone suffices? I am having a hard time figuring it out.

And if B is indeed the answer, I don't this this is a sub 600 question.

prasun9 · Answer

The question asks Volume(A) is how much more than Volume(B). 
The answer can be either:
a) Volume(A) is X more than Volume(B)
b) Volume(A) is X% more than Volume(B).

Stmt I - Clearly not sufficient as we know nothing about cylinder A

Stmt II -  \frac{Volume(A)}{Volume(B)} = \frac{4}{7}

Subtract 1 from both sides

\frac{Volume(A)}{Volume(B)} - 1 = \frac{4}{7} - 1 
 \frac{Volume(A) - Volume(B)}{Volume(B)} = \frac{4 - 7}{7}

Multiply both sides by 100

\frac{Volume(A) - Volume(B)}{Volume(B)} * 100 = \frac{4 - 7}{7} * 100

Now left hand side gives "The  % value  of volume of cylinder A is how much more than the volume of cylinder B"
Hence Stmt II is sufficient.

eshan429 · Answer

The question is

The volume of cylinder A is how much more than the volume of cylinder B if cylinder A has x+4 radius and cylinder B has a height of 4?

What you are calculating is the percentage. They are  NOT  the same thing.

Volume of A could be  4  and that of B could be  7 . The difference will be  3 .

or

Volume of A could be  40  and that of B could be  70 . The difference will be  30 .

So, statement B alone is   not   sufficient.

Whereas if you combine both A and B, we get the answer without using anything in the question stem.

So, in my opinion, the answer should be C and not B.

DangerPenguin · Answer

This is what I was thinking:

statement 1) not sufficient because you still don't know the value of x to calculate cylinder A's volume
statement 2) sufficient because you can pick numbers and find out how much larger cylinder A is than cylinder B

eshan429 · Answer

Can you please demonstrate how?

Ashishmathew01081987 · Answer

I am getting "C" as the answer :

first of all the question asks " The volume of cylinder A is how much more than the volume of cylinder B " and not the % difference. Moreover, ratio is a relative term and we cannot reach a definite answer unless we have a definite concrete term. If we try to get an answer with the current question, ultimately we end up with two unknowns i.e. Radius of Cyl A and Height of Cyl A. So B is definitely not the answer. We can get "C" as the answer but then the data given in the question becomes irrelevant. 
Its a bit confusing because % difference ca be found out by Stat B alone.

Please explain why B is the answer. Did I miss something important to consider ????

DangerPenguin · Answer

You are correct the answer should be C!

The volume of cylinder A is how much more than the volume of cylinder

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Data Sufficiency (DS) Questions

The volume of cylinder A is how much more than the volume of cylinder

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards