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# Water is pumped into a partially filled tank at a constant

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Math Expert
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Water is pumped into a partially filled tank at a constant  [#permalink]

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06 Aug 2012, 02:09
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5% (low)

Question Stats:

90% (00:55) correct 10% (01:04) wrong based on 1855 sessions

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Water is pumped into a partially filled tank at a constant rate through an inlet pipe. At the same time, water is pumped out of the tank at a constant rate through an outlet pipe. At what rate, in gallons per minute, is the amount of water in the tank increasing?

(1) The amount of water initially in the tank is 200 gallons.
(2) Water is pumped into the tank at a rate of 10 gallons per minute and out of the tank at a rate of 10 gallons every $$2\frac{1}{2}$$ minutes.

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Re: Water is pumped into a partially filled tank at a constant  [#permalink]

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06 Aug 2012, 02:09
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SOLUTION

Water is pumped into a partially filled tank at a constant rate through an inlet pipe. At the same time, water is pumped out of the tank at a constant rate through an outlet pipe. At what rate, in gallons per minute, is the amount of water in the tank increasing?

(1) The amount of water initially in the tank is 200 gallons. Clearly insufficient.
(2) Water is pumped into the tank at a rate of 10 gallons per minute and out of the tank at a rate of 10 gallons every $$2\frac{1}{2}$$ minutes. Since water is pumped out of the tank at a rate of 10 gallons every $$2\frac{1}{2}=\frac{5}{2}$$ minutes, then it's pumped out at a rate of $$\frac{10}{(\frac{5}{2})}=4$$ gallons per minute, hence the net increase is $$10-4=6$$ gallons per minute. Sufficient.

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Re: Water is pumped into a partially filled tank at a constant  [#permalink]

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27 Apr 2016, 04:39
Statement 1 gives the initial capacity of the tank, clearly insufficient
statement 2 gives both the rate of inflow as well as outflow which is sufficient to calculate the rate at which water is increasing per minute in the tank
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Re: Water is pumped into a partially filled tank at a constant  [#permalink]

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30 Jul 2016, 07:25
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Bunuel wrote:
Water is pumped into a partially filled tank at a constant rate through an inlet pipe. At the same time, water is pumped out of the tank at a constant rate through an outlet pipe. At what rate, in gallons per minute, is the amount of water in the tank increasing?

(1) The amount of water initially in the tank is 200 gallons.
(2) Water is pumped into the tank at a rate of 10 gallons per minute and out of the tank at a rate of 10 gallons every $$2\frac{1}{2}$$ minutes.

We are given that water is flowing into a tank through an inlet pipe and out of the tank through an outlet pipe. We need to determine at what rate the amount of water in the tank is increasing.

Statement One Alone:

The amount of water initially in the tank is 200 gallons.

Knowing the initial amount of water in the tank is not enough information to determine at what rate the amount of water in the tank is increasing. Statement one alone is not sufficient to answer the question. We can eliminate answer choices A and D.

Statement Two Alone:

Water is pumped into the tank at a rate of 10 gallons per minute and out of the tank at a rate of 10 gallons every 2.5 minutes.

From statement two, we know the rate at which the water is flowing into the tank and also the rate at which the water is flowing out of the tank. With this information we can determine the “net rate,” or the rate at which the amount of water is increasing in the tank. The formula is: rate = work/time

rate in = 10/1 = 10 gallons per minute

rate out = 10/2.5 = 4 gallons per minute

Thus, the amount of water is increasing in the tank at a rate of 10 – 4 = 6 gallons per minute.

Statement two alone is sufficient to answer the question.

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Re: Water is pumped into a partially filled tank at a constant  [#permalink]

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30 Sep 2016, 22:14
Got the correct answer B in 42 seconds.
No need to solve any thing in these type of Questions.
Clearly A is not sufficient and you can mark this within 20 Sec.
B gives Inflow and Outflow rate and Question is asking the Increasing Rate not the Increasing values.

People might get confused to mark C in this Question but the trick here is Question is asking for Rate of Increase not the Exact values of how much its is increased.

Hope this will help Someone..
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Water is pumped into a partially filled tank at a constant  [#permalink]

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05 Apr 2018, 07:33
Statement - 1:
We know that we have 200 gallons of water in the tank but this doesn't help us much - Clearly Insufficient
Statement - 2:
Remember: Rates (work rates) are additive.

In this case we have a positive work (water-in) and a negative work (water-out), however we need to ensure that before we add (or subtract) the rates, both the rates need to have the same work-time relationship.

At this stage, we are done. We don't really need to calculate anything and we can safely say that this statement is clearly sufficient. In case you want to know the math then here goes: First we need to agree that we have an overall positive work since the rate of water-in is more than the rate of water-out.

Tip: For work / rate problems, it is always a good trick to create a table listing down all the metrics namely worker, rate, time, and work done:
Water is pumped into a partially filled tank at a constant &nbs [#permalink] 05 Apr 2018, 07:33
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