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

Redeem

Cube or not

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 229
Joined: Tue Jan 13, 2009 6:56 am
Thanked: 8 times
GMAT Score:700

Cube or not

by Uri » Fri May 08, 2009 3:18 am
The base of a rectangular block has area 60 sq.cm. Is the block a cube?

1. The area of the front face of the block is 60 sq.cm
2. The area of the side face of the block is 60 sq.cm

Source: Kaplan
OA: [spoiler](C)[/spoiler]

Please explain your logic.
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 » Fri May 08, 2009 9:26 am
Look at it this way: you have a rectangular block with length = a, width = b and height = c. What you need to do is prove that a = b = c.

Now, you start with the fact that its base is 60, meaning that ab = 60.

1. tells you that the front face is also 60, meaning that ac = 60 as well. So you have that:
ac = 60
ab = 60

The only extra info you have is that c = b, but we don't know if a is or is not equal to the the two. For all we know, b = c = 12 and a = 5. So 1 isn't enough.

2. basically is the same as 1, just with a bit of variation: here you have that bc = ab = 60, meaning that a = c. Again, it's not enough since you need to have a relationship between all three sides.

But put the two together and you get that:
b = c
a = c

This means that, in the end, a = b = c, making the rectangular block a cube. So C is indeed the answer.
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 229
Joined: Tue Jan 13, 2009 6:56 am
Thanked: 8 times
GMAT Score:700

by Uri » Fri May 08, 2009 12:34 pm
thanks a lot, DanaJ. ur explanation is more lucid than the official one :)
Top
Post new topic Post Reply
• Page 1 of 1