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# How many kiloliters of water are in a reservoir?

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Math Expert
Joined: 02 Sep 2009
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How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 08:36
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45% (medium)

Question Stats:

50% (00:33) correct 50% (00:41) wrong based on 102 sessions

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How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 08:47
1
Let Capacity of reservoir = C
Let number of KL of water in reservoir = W

1. If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
C = W + 430

Not sufficient

2.The reservoir is normally 65 percent full.
Normal water quantity = 65% of C

Not sufficient

Combining 1 and 2,
We don't know whether we have normal water levels in statement 1 .
Hence , not sufficient.
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How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 08:51
1
Bunuel wrote:
How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

Target question: How many kiloliters of water are in a reservoir?

Statement 1: If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
So, currently, there are 430 kiloliters of EMPTY SPACE in the reservoir.
Since, we have no idea of how much water is currently in the reservoir, we cannot determine the TOTAL volume of water in the reservoir.
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: The reservoir is normally 65 percent full
Knowing the PROPORTION of water in the reservoir cannot help determine the TOTAL volume of water in the reservoir.
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 2 says, "The reservoir is normally 65 percent full"
This statement has some problematic wording that affects the two statements combined.
Does this mean that the reservoir is CURRENTLY 65 percent full? Not really.
If we don't know what percent of the reservoir is CURRENTLY full, then the combined statements are NOT SUFFICIENT, and the answer is E

If we are saying that the reservoir is CURRENTLY 65 percent full, then we know that 35% of the reservoir is EMPTY SPACE.
Statement 1 tells us that there are 430 kiloliters of EMPTY SPACE in the reservoir.
So, 35% of the total volume = 430
In other words, 0.35(total volume) = 430
Since we COULD solve this equation, we COULD determine the TOTAL volume of water in the reservoir,

the Since we can answer the target question with certainty, the combined statements are SUFFICIENT in which case the combined statements are SUFFICIENT, and the answer is C

Cheers,
Brent
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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 10:05
Bunuel wrote:
How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

Let, current quantity of water = X (this needs to be found)
Let, the capacity of the reservoir = C

S1)
$$X + 430 = C$$
$$X = C - 430$$
We do not know C therefore X cannot be found- Insufficient

S2)
Normally 65% full.
(Now, this Normally is debatable. Since this in not a CR question, i will assume that today is a normal day. And the reservoir is 65% currently. )
since we do not have any info about the capacity, we cannot say how much is 65%. - Insufficient

S1+S2)
From S2-The reservoir is 65% full => 35% empty
From S1-To completely fill it, we need 430 more
Therefore,
$$35$$% of Capacity$$= 430$$
$$.35*C = 430$$

We can obtain C (capacity) from here. Substituting in S1, we can get X. - Sufficient

Please correct me if im wrong.
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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 18:15
Bunuel wrote:
How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

With already shown calculations, we can derive that we can have two answers in this case C or E. On a test day, i will mark it E as i have heard from lot of experts that GMAt tests aptitude in Quant also.

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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 18:28
Praveengeol wrote:
Bunuel wrote:
How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

With already shown calculations, we can derive that we can have two answers in this case C or E. On a test day, i will mark it E as i have heard from lot of experts that GMAt tests aptitude in Quant also.

In GMAT, the wording of the questions will not be ambiguous. It is not about C or E. If in the GMAT you happen to be convinced that 2 of the 5 choices "appear" to be correct , then you must recheck your calculations as official GMAT questions will always have 1 and only 1 correct and unambiguous answer.
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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 19:18
Engr2012 wrote:
Praveengeol wrote:
Bunuel wrote:
How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

With already shown calculations, we can derive that we can have two answers in this case C or E. On a test day, i will mark it E as i have heard from lot of experts that GMAt tests aptitude in Quant also.

In GMAT, the wording of the questions will not be ambiguous. It is not about C or E. If in the GMAT you happen to be convinced that 2 of the 5 choices "appear" to be correct , then you must recheck your calculations as official GMAT questions will always have 1 and only 1 correct and unambiguous answer.

Thank You expert Engr. But what about this question, what should be the approach? This question is coming from Buneuel, The Bunuel, i am sure it can appear in GMAT as well.
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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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02 Nov 2015, 22:21
1
Hi,

We can not consider normal capacity to be 65%. We do not have a definite indication on this.

Despite using both the statements, one can not arrive at the solution.

Hence the choice is E.

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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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08 Nov 2015, 05:53
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

How many kiloliters of water are in a reservoir?

(1) If the reservoir were filled to capacity, there would be 430 more kiloliters in the reservoir.
(2) The reservoir is normally 65 percent full.

There are 2 variables (x: original volume, c:capacity of reservoir), and 2 equations are given from the 2 conditions, so there is high chance (C) will be our answer.
If we look at the conditions together,
x+430=c, x=0.65c. The condition is sufficient, so the answer becomes (C).

For cases where we need 2 more equation, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.
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Re: How many kiloliters of water are in a reservoir?  [#permalink]

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08 Oct 2017, 05:53
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