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An empty pool being filled with water at a constant rate tak [#permalink]
07 Feb 2011, 00:20

00:00

A

B

C

D

E

Difficulty:

15% (low)

Question Stats:

81% (01:58) correct
18% (00:55) wrong based on 223 sessions

An empty pool being filled with water at a constant rate takes 8hours to fill to 3/5 of its capacity.how much more time will it take to finish filling the pool?

A. 5hr 30min B. 5hr 20min C. 4hr 48min D. 3 hr 12min E. 2hr 40 min

An empty pool being filled with water at a constant rate takes 8hours to fill to 3/5 of its capacity. how much more time will it take to finish filling the pool? a)5hr 30min b)5hr 20min c)4hr 48min d)3 hr 12min e) 2hr 40 min

As pool is filled to 3/5 of its capacity then 2/5 of its capacity is left to fill.

To fill 3/5 of the pool took 8 hours --> to fill 2/5 of the pool will take 8/(3/5)*2/5=16/3 hours = 5 hours 20 minutes (because if t is the time needed to fill the pool then t*3/5=8 --> t=8*5/3 hours --> to fill 2/5 of the pool 8*5/3*2/5=16/3 hours will be needed).

Or plug values: take the capacity of the pool to be 5 liters --> 3/5 of the pool or 3 liters is filled in 8 hours, which gives the rate of 3/8 liters per hour --> remaining 2 liters will require: time = job/rate = 2/(3/8) = 16/3 hours = 5 hours 20 minutes.

An empty pool being filled with water at a constant rate takes 8hours to fill to 3/5 of its capacity. how much more time will it take to finish filling the pool? a)5hr 30min b)5hr 20min c)4hr 48min d)3 hr 12min e) 2hr 40 min

As pool is filled to 3/5 of its capacity then 2/5 of its capacity is left to fill.

To fill 3/5 of the pool took 8 hours --> to fill 2/5 of the pool will take 8/(3/5)*2/5=16/3 hours = 5 hours 20 minutes (because if t is the time needed to fill the pool then t*3/5=8 --> t=8*5/3 hours --> to fill 2/5 of the pool 8*5/3*2/5=16/3 hours will be needed).

Or plug values: take the capacity of the pool to be 5 liters --> 3/5 of the pool or 3 liters is filled in 8 hours, which gives the rate of 3/8 liters per hour --> remaining 2 liters will require: time = job/rate = 2/(3/8) = 16/3 hours = 5 hours 20 minutes.

Answer: B.

Thanks Bunuel using this capacity left to fill in solution i can save time
_________________

The proof of understanding is the ability to explain it.

An empty pool being filled with water at a constant rate takes 8 hours to fill to 3/5 of its capacity. How much more time will it take to finish filling the pool ?

5hr 30 min 5hr 20 min 4hr 48 min 3hr 12 min 2hr 40min

Sol: Rate = (3/5 capacity) / 8 hours = (2/5 capacity) / x hours solving for x : x = 80/15 = 5.3333 hr i selected A which is 5hrs 30 min but original answer is 5hrs 20min . Whats going wrong ?? isn't it 5.333... is 5hrs 30min when rounded off ??
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Re: An empty pool being filled with water at a constant rate tak [#permalink]
05 Jun 2013, 14:04

I did this a little differently. It takes 480 mins to fill 3/5 of the pool. We're trying to find out how long it'll take for the remaining 2/5. I solved how many minutes it'll take to fill the pool to 1/5 capacity and multiplied it by 2. 480 / 3 = 160 mins (1/5 full) 160 * 2 = 320 mins (2/5 full) 320 mins = 5 hours 20 mins

Re: An empty pool being filled with water at a constant rate tak [#permalink]
12 Sep 2013, 10:31

An empty pool being filled with water at a constant rate takes 8hours to fill to 3/5 of its capacity.how much more time will it take to finish filling the pool?

A. 5hr 30min B. 5hr 20min C. 4hr 48min D. 3 hr 12min E. 2hr 40 min

Sol: work done in 1 hour: (3/5)/8 = 3/40

how much is left? (2/5)

Therefore, hours taken to complete this: (3/5)/(3/40) = 80/15 = 5 hours + (5/15) mins

5/15 in minutes = 5*4/15*4 = 20/60.

So, the answer is, 5 hrs 20 mins.

gmatclubot

Re: An empty pool being filled with water at a constant rate tak
[#permalink]
12 Sep 2013, 10:31