BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Volume vs Area of Sphere

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Sun Feb 22, 2009 11:27 pm
GMAT Score:600

Volume vs Area of Sphere

by hijazim » Sun Mar 01, 2009 6:30 am
Image

This question has a wording problem. If I am not wrong the volume should be 4/3*pi*r^3 and not 4/3*pi*r^-3.

Any help please. The OA is D. But I couldn't interpret how???
Top
Source: — Data Sufficiency |
User avatar
Site Admin
Posts: 2567
Joined: Thu Jan 01, 2009 10:05 am
Thanked: 712 times
Followed by:550 members
GMAT Score:770

by DanaJ » Sun Mar 01, 2009 6:39 am
You are right, that (-3) does not belong there. It may be a typo, it's surely not correct. Check Wikipedia when in doubt! :D
Now, back to the question: it says here that the volume of the sphere is 972Pi, which will be (4/3)*Pi*(r^3):
972 = 1000 - 28 = 4*250 - 4*7 = 4*243
So you have that (4/3)*(r^3) = 4*243
This makes r^3 = 243*3 = 729 or 9^3, making r = 9.

This means that the total surface area will be 4Pi(r^2) = 4*81*Pi = 324Pi.
Since my answer is consistent with the OA, it was indeed just a typo.
Top
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Sun Feb 22, 2009 11:27 pm
GMAT Score:600

by hijazim » Sun Mar 01, 2009 6:57 am
Yes man, this is it. Thanks for sharing :)
Top
Post new topic Post Reply
• Page 1 of 1