GMAT Practice Question (One of Hundreds)
A computer has three hard-drives; the smallest and largest hard-drives account for 25 and 45 percent of the total storage space on the computer, respectively; due to a catastrophic error, the largest hard-drive lost approximately 22% of its storage space; after this error, the hard drive that was originally the second largest accounts for approximately what percent of the total hard-drive space on the reduced computer?
Correct Answer: B
Use the following equation: 25% + 45% + medium hard drive = 100%
- Since there are only three hard drives and these account for 100% of the space on the computer, you can write the following equation:
(Smallest Hard Drive) + (Medium Hard Drive) + (Large Hard Drive) = 100%
25% + (Medium Hard Drive) + 45% = 100%
- You now know the size of the medium hard drive:
(Medium Hard Drive) = 30%
- If the largest hard-drive lost approximately 22% of its storage space, it now accounts for (1-.22)(.45) = .351 or 35.1% of the old total space.
- You can now find what percent of the total hard-drive space the second largest hard drive accounts for:
= (Drive Originally 2nd Largest) / (New Total Drive Space)
= 30%/(35.1%+25% + 30%) = 30%/90% = ~ 33%
- If the concept of manipulating and dividing percents throws you off, this is an excellent problem to pick numbers on. Simply let the percents be actual hard-drive space. In other words, set the total hard drive space to be 100GB. Then, the smallest hard-drive is 25GB, the medium hard-drive is 30GB, and the largest is 45GB. After the largest shrinks by 22%, it is now 45*(1-.22) = 35GB. So, the reduced hard drive is 25+30+35 = 90GB and the second largest hard drive is 30GB/90GB = 33%.