OG2015 DS A circular tub has
This topic has expert replies
- lionsshare
- Senior | Next Rank: 100 Posts
- Posts: 62
- Joined: Wed Aug 09, 2017 3:54 pm
GMAT/MBA Expert
- Jay@ManhattanReview
- GMAT Instructor
- Posts: 3008
- Joined: Mon Aug 22, 2016 6:19 am
- Location: Grand Central / New York
- Thanked: 470 times
- Followed by:34 members
You must know that the surface area of a cylinder (circular tub) equals to 2Ï€rh, where r = radius of the cylinder and h = height of the cylinder
Mind that we need not calculate the surface area of a cylinder (circular tub); we are asked to calculate the surface area of the painted band. So, let's treat the band as a small cylinder having its radius = radius of the cylinder = r, and height = x.
Thus, the surface area of the band = 2Ï€rx
If we get the values of r and x, we get the answer.
Statement 1: x = 0.5 meter
It can't help, we do not have any information about the radius, r. Insufficient.
Statement 2: The height of the tub is 1 meter.
This does not help either. We are concerned about the height of the painted band, and not the height of the tub. Insufficient.
Statement1 & 2:
Even after combining the two statements, we do not get the value of r. Insufficient.
The correct answer: E
Hope this helps!
Download free ebook: Manhattan Review GMAT Quantitative Question Bank Guide
-Jay
__________________________________
Manhattan Review GMAT Prep
Locations: New York | Warsaw | Cape Town | Madrid | and many more...
Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
GMAT/MBA Expert
- Jeff@TargetTestPrep
- GMAT Instructor
- Posts: 1462
- Joined: Thu Apr 09, 2015 9:34 am
- Location: New York, NY
- Thanked: 39 times
- Followed by:22 members
We are given a cylinder with a shaded band painted around its circumference. We know that the height of the band is x meters, and we also know that the shape of the band is a hollow cylinder (i.e., a cylinder without the top and bottom circular bases). We need to determine the surface area of the band. We know the surface area of a cylinder (when it has the top and bottom circular bases) is:
surface area = 2Ï€r^2 + 2Ï€rh
Notice that the 2Ï€r^2 is the area of the two circular bases of the cylinder (had it been a solid one). However, here the cylindrical band is hollow, thus its surface area is:
surface area = 2Ï€rh
We can replace h with x since that is the height of the band, so we have:
surface area of band = 2Ï€rx
So if we can determine the value of r and x, we can determine the surface area of the band.
Statement One Alone:
x = 0.5
While we have the value of x, without knowing the value of r, we cannot determine the surface area of the band. Statement one is not sufficient to answer the question.
Statement Two Alone:
The height of the tub is 1 meter.
Knowing the height of the tub does not provide us with the value of x or r. Statement two is not sufficient to answer the question.
Statements One and Two Together:
Using statements one and two together we still do not have a value for r and thus we cannot determine the surface area of the band.
Answer: E
Jeffrey Miller
Head of GMAT Instruction
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews