The shaded face of cube C, shown here, has an area...

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BTGmoderatorLU: Moderator; Posts: 2505; Joined: Sun Oct 15, 2017 1:50 pm; Followed by:6 members

The shaded face of cube C, shown here, has an area...

by BTGmoderatorLU » Tue Dec 26, 2017 3:13 pm

The shaded face of cube C, shown here, has an area of 49 squares inches. What is the volume of Cube C in cubic inches?

A. 7
B. 28
C. 84
D. 343
E. 364

The OA is D.

I'm confused with this PS question, can I say that L^2=49 and then the volume of C=7^3=343?

Experts, any suggestion? Thanks in advance.

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Source: Beat The GMAT — Problem Solving | Tue Dec 26, 2017 3:13 pm

elias.latour.apex: Master | Next Rank: 500 Posts; Posts: 228; Joined: Thu Apr 20, 2017 1:02 am; Location: Global; Thanked: 32 times; Followed by:3 members; GMAT Score:770

A simple solution path

by elias.latour.apex » Wed Dec 27, 2017 4:45 am

Since it is a cube, all sides of the cube are equal.
Since the area of one face is 49, each side must be 7.
Therefore, the volume of the cube will be 49x7, which is the same as 7^3.

Since the units digit of the answer will be a 3, and since only answer choice D fits that criterion, it is not necessary to do all the math.

Elias Latour
Verbal Specialist @ ApexGMAT
blog.apexgmat.com
+1 (646) 736-7622

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Wed Sep 04, 2019 5:21 pm

BTGmoderatorLU wrote:

The shaded face of cube C, shown here, has an area of 49 squares inches. What is the volume of Cube C in cubic inches?

A. 7
B. 28
C. 84
D. 343
E. 364

The OA is D.

I'm confused with this PS question, can I say that L^2=49 and then the volume of C=7^3=343?

Experts, any suggestion? Thanks in advance.