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pravinpillai2015
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Working at constant rate, pump X pumped out half of the water in a flo Updated on: 02 Aug 2016, 00:17
Originally posted by pravinpillai2015 on 01 Aug 2016, 21:06.
Last edited by Bunuel on 02 Aug 2016, 00:17, edited 1 time in total.
RENAMED THE TOPIC.
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E
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Working at constant rate, pump X pumped out half of the water in a flooded basement in 4 hours. The pump Y was started and the two pumps, working independently at their respective constant rates, pumped out rest of the water in 3 hours. How many hours would it have taken pump Y , operating alone at its own constant rate, to pump out all of the water that was pumped out of the basement?

a. 10
b. 12
c. 14
d. 18
e. 24
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Working at constant rate, pump X pumped out half of the water in a flo 02 Aug 2016, 12:33
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rate of x=1/8
rate of x+y=1/6
rate of y=1/6-1/8=1/24
24 hours
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Working at constant rate, pump X pumped out half of the water in a flo 01 Aug 2016, 23:35
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Here pump x was able to work 1/2 the job in 4 hrs.

so it would have taken the pump x to complete the task in 8 hrs. so 1/x=1/8.....eqn(1)

again x and y working independently doing the same work (1/2 of the work) take 3hrs.
so total task would take 6 hrs. 1/x+1/y=1/6.........eqn(2)

solve eqn 1 and eqn 2 to get y=24
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Working at constant rate, pump X pumped out half of the water in a flo 02 Aug 2016, 00:19
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pravinpillai2015
Working at constant rate, pump X pumped out half of the water in a flooded basement in 4 hours. The pump Y was started and the two pumps, working independently at their respective constant rates, pumped out rest of the water in 3 hours. How many hours would it have taken pump Y , operating alone at its own constant rate, to pump out all of the water that was pumped out of the basement?

a. 10
b. 12
c. 14
d. 18
e. 24



Almost the same question to practice: https://gmatclub.com/forum/working-alon ... 16023.html

Hope it helps.
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Working at constant rate, pump X pumped out half of the water in a flo 21 Jan 2018, 13:01
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pravinpillai2015
Working at constant rate, pump X pumped out half of the water in a flooded basement in 4 hours. The pump Y was started and the two pumps, working independently at their respective constant rates, pumped out rest of the water in 3 hours. How many hours would it have taken pump Y , operating alone at its own constant rate, to pump out all of the water that was pumped out of the basement?

a. 10
b. 12
c. 14
d. 18
e. 24


If the pump X pumped out half the water in 4 hours, it will pump out the entire water in 8 hours.
Similarly, the pump Y was started and the two pumps operating together are able to pump out
the entire water in 3 hours.

Assume the total capacity of the pump to be 96 units.

So, the pump X must be pumping out 12 units/hour. Since, both the pumps working together
pump out the remainder of the water in 3 hours, their combined capacity will be 16 units/hour.
Hence, pump Y must be pumping out 4 units/hour.

Therefore, Pump Y alone will take \(\frac{96}{4}\) = 24 hours(Option E)
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Working at constant rate, pump X pumped out half of the water in a flo 15 Feb 2018, 09:56
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Suppose X extracts x liters/hour, while Y extracts y liters/hour
In 4 hours, X extracts 4 x liters
This is half of the basement capacity. So, total volume of water in the basement = 8x liters

After 4 hours, Y was started as well. They flush the remaining 4 x in 3 hours.

In 3 hours, X and Y combined would flush 3*(x + y)

It is given that 3*(x + y) = 4x
This gives x = 3y

Operating alone how much would Y take?

Total water = 8x
Y's capacity = y liters/hour

So, time taken by Y = 8x/y

We know x = 3y
So, x/y = 3

So, time taken by Y = 8x/y = 8*3 = 24
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Working at constant rate, pump X pumped out half of the water in a flo 22 Apr 2019, 15:34
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pravinpillai2015
Working at constant rate, pump X pumped out half of the water in a flooded basement in 4 hours. The pump Y was started and the two pumps, working independently at their respective constant rates, pumped out rest of the water in 3 hours. How many hours would it have taken pump Y , operating alone at its own constant rate, to pump out all of the water that was pumped out of the basement?

a. 10
b. 12
c. 14
d. 18
e. 24

Trying plugging:

We are looking at half capacities throughout the problem, so we could half the answer choices for simplicity. If X = 4h -> rate = 1/4; X + Y = 3h -> rate = 1/3. We can start plugging answer choices from B:


B: 12 -> 6 h -> 1/6 + 1/4 = 5/12 - almost 1/2 or too big for the 1/3 we need, that means we need a smaller Y rate or higher Y hours
D: 18 -> 9 h -> 1/9 + 1/4 = 13/36 - if we compare with 1/3 or 13/39, 13/ 36 is still a bit big, but closer to what we need -> answer E
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Working at constant rate, pump X pumped out half of the water in a flo 12 Jan 2021, 22:01
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A alternative approach:

We can infer that x takes 8 hours to remove water completely, now:

We see that X worked 7 hours - 4+3 hours, and was left with only one hours of work.

For that 1 hour of work Y took 3 hours, so for 8 hours of X's work Y will take 8*3 = 24 hours
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Working at constant rate, pump X pumped out half of the water in a flo 21 Jun 2023, 03:09
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pump x was able to do 1/2 of the job in 4 hrs
pump x would do the entire work alone in 1/8 hrs
therefore, 1/x = 1/8 --- eqn (1)

since x and y are now working together, they finish the entire thing in 3 hrs
total time taken would be 6 hrs

pump x + pump y = 1/x + 1/y= 1/6 ---- eqn (2)

1/8+ 1/y = 1/6
1/y = 1/6- 1/8
1/y = 8-6/48
1/y = 1/24

therefore, y = 24
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Working at constant rate, pump X pumped out half of the water in a flo 19 Jul 2024, 03:15
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Hello from the GMAT Club BumpBot!

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