The flow of water through a drainage pipe was monitored for

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BTGmoderatorLU: Moderator; Posts: 2650; Joined: Sun Oct 15, 2017 1:50 pmFollowed by: 6 members

by BTGmoderatorLU » Fri Jun 01, 2018 2:40 pm

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The flow of water through a drainage pipe was monitored for a 3-hour period. In the second hour, the rate of flow was 15 gallons per hour, which was 50 percent faster than the rate of flow for the first hour. If 25 percent more water flowed through the pipe in the third hour than it did in the second, how many gallons of water flowed through the pipe during the entire three hours?

A. 41.25
B. 42.5
C. 43.75
D. 45.0
E. 57.5

The OA is C.

Please, can anyone assist me with this PS question? I'm confused. Thanks in advance!

Source: Beat The GMAT — Problem Solving | Fri Jun 01, 2018 2:40 pm

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Fri Jun 01, 2018 11:07 pm

BTGmoderatorLU wrote:The flow of water through a drainage pipe was monitored for a 3-hour period. In the second hour, the rate of flow was 15 gallons per hour, which was 50 percent faster than the rate of flow for the first hour. If 25 percent more water flowed through the pipe in the third hour than it did in the second, how many gallons of water flowed through the pipe during the entire three hours?

A. 41.25
B. 42.5
C. 43.75
D. 45.0
E. 57.5

Let F = the first hour and T = the third hour.

Since the second-hour rate is 50% faster than the first-hour rate, the second-hour rate (15 gallons) is 150% of the first-hour rate:
15 = (150/100)F
15 = (3/2)F
30 = 3F
F = 10 gallons.

Since 25% more water flows during the third hour than during the second hour, the number of gallons that flows during the third hour is 125% of the 15 gallons that flow during the second hour:
T = (125/100)15 = (5/4)15 = 75/4 = 18.75.

Total amount of water = 15 + 10 + 18.75 = 43.75.

The correct answer is C.

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