A water pump began

stevecultt wrote:A water pump began filling an empty swimming pool with water and ran at a constant rate til the swimming pool was full. At some time, the pool was 1/2 full, and 2 1/3 hours later, it was 5/6 full. How many hours would it take the pump to fill the empty pool completely?

(A) 4
(B) 5 1/3
(C) 7
(D) 7 1/5
(E) 8 1/3

OA C

According to the given data, the pump filled (5/6 – 1/2) = 1/3 part of the pool in 2 1/3 = 7/3 hours

Thus, time taken by the pump to fill the entire pool = (7/3) ÷ (1/3) = (7/3) / (1/3) = 7 hours

Thus, the time taken by the pump to fill the empty pool completely = 7 hours

The correct answer: C

Hope this helps!

Download free ebook: Manhattan Review GMAT Quantitative Question Bank Guide

-Jay
_________________
Manhattan Review GMAT Prep

Locations: New York | Bangkok | Abu Dhabi | Rome | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.

Hi stevecultt,

We're told that a water pump took a certain amount of time to fill 1/2 of an empty pool, then 2 1/3 hours later, the pool was 5/6 full. We're asked for the number of hours it would take to fill the empty pool completely. This question can be solved by TESTing THE ANSWERS.

Let's TEST Answer C: 7 hours

IF... it takes 7 hours to fill the pool, then...
it the pump fills 1/7 of the pool each hour.
The pump would need (7)(5/6) = 35/6 hours to fill 5/6 of the pool

It take 3.5 hours = 7/2 hours to fill half of the pool
7/2 hours + 2 1/3 hours = 7/2 + 7/3 = 21/6 + 14/6 = 35/6 hours
This is an exact MATCH for what we were told, so this MUST be the answer.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

stevecultt wrote: ↑

Wed Jul 19, 2017 1:01 am

A water pump began filling an empty swimming pool with water and ran at a constant rate til the swimming pool was full. At some time, the pool was 1/2 full, and 2 1/3 hours later, it was 5/6 full. How many hours would it take the pump to fill the empty pool completely?

(A) 4
(B) 5 1/3
(C) 7
(D) 7 1/5
(E) 8 1/3

OA C

Solution:

Since it took 7/3 hours to fill 5/6 - 3/6 = 2/6 = 1/3 of the pool.

The rate is:

(1/3) / (7/3) = 1/7.

So, it takes 1/(1/7) = 7 hours to fill the pool.

Alternate Solution:

It took 2 ⅓ - ½ = 7/3 hours to fill 5/6 - 3/6 = 2/6 = 1/3 of the pool. We can set up a proportion, letting x = the number of hours to completely fill the pool:

(7/3) / (⅓) = x / 1

Cross-multiplying, we obtain:

x/3 = 7/3

x = 7. Thus, it takes 7 hours to fill the pool.

Answer: C