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

Redeem

geometry area ratio

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 275
Joined: Wed Jul 02, 2008 4:19 am
Thanked: 4 times

geometry area ratio

by Xbond » Tue Apr 14, 2009 12:00 pm
Hi

Could you help me to resolve this goemetry problem ?


What is the ratio of the surface area of a cube to the surface area of a rectangular solid identical to the cube in all ways except that its length has been doubled ?

regards,
Top
Source: — Problem Solving |
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 » Tue Apr 14, 2009 12:48 pm
Say a = length of side of cube. Then you get that the cube has 6 sides of area A = a^2, so the total area of the cube will be 6a^2.

Now think of the rectangular solid: the cube's length has been modified, so you get basically 4 sides that have been changed and 2 that haven't. Your surface area will be 4*2a^2 + 2*a^2 = 10 a^2.

So the ratio will be 6a^2/10a^2 = 6/10 = 3/5.

Please forgive my bad drawing....
Attachments
Untitled.jpg
Top
Post new topic Post Reply
• Page 1 of 1