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# In a certain zoo, 9L of water can sustain 5 monkeys

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Joined: 13 Oct 2016
Posts: 298
GMAT 1: 600 Q44 V28
In a certain zoo, 9L of water can sustain 5 monkeys [#permalink]

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17 May 2017, 13:15
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KUDOS
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Difficulty:

25% (medium)

Question Stats:

68% (00:44) correct 32% (00:40) wrong based on 50 sessions

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In a certain zoo, 9 Liters of water can sustain 5 monkeys. What is the maximum number of monkeys 16 Liters of water can sustain?

A. 3
B. 8
C. 9
D. 28
E. 29
[Reveal] Spoiler: OA

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Last edited by Kritesh on 21 May 2017, 02:17, edited 1 time in total.
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Re: In a certain zoo, 9L of water can sustain 5 monkeys [#permalink]

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18 May 2017, 07:35
Kritesh wrote:
In a certain zoo, 9 Liters of water can sustain 5 monkeys. What is the maximum number of monkeys 16 Liters of water can sustain?

A. 3
B. 8
C. 9
D. 28
E. 29

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If you appreciate the question then please click +1Kudos

Set up a ratio, then a proportion. Let x be maximum number of monkeys.

9 liters of water can sustain 5 monkeys ==> 9 liters for 5 monkeys = $$\frac{9}{5}$$

Maximum number of monkeys that 16 liters can sustain ==> $$\frac{16}{x}$$

$$\frac{9}{5}$$ = $$\frac{16}{x}$$

Cross multiply to get 9x = 80

Careful here: 9 goes into 80 only 8 times. 9*9=81, too high, there's not enough water for the 9th monkey. Answer:

[Reveal] Spoiler:
B
Hope it helps.
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Re: In a certain zoo, 9L of water can sustain 5 monkeys [#permalink]

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20 May 2017, 01:10
Number of people/animals etc 'N' always vary Directly with the amount of resources 'R'.
(more the people more the resources required and vice versa).

When two quantities vary Directly, Ratio of change of first (or percentage change in first) has to be equal to the ratio of change of second (or percentage change in second)..

So N1/N2 = R1/R2.
given R1=9, R2=16, N1=5, find N2

5/N2 = 9/16. Solve to get N2=80/9 = 8.88..

We cannot round it up to 9, as any number more than 8.88.. would require more than 16 litres of water.
So MAX 8 monkeys can be sustained.

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Re: In a certain zoo, 9L of water can sustain 5 monkeys [#permalink]

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20 May 2017, 03:28
In a certain zoo, 9 Liters of water can sustain 5 monkeys. What is the maximum number of monkeys 16 Liters of water can sustain?

9 Liters of water is used by 5 monkeys
Let Maximum number of monkeys who can use 16 Liters of water = X
9 Liters ----- 5 monkeys
16 Liters ---- X
By Cross multiplying we get, $$\frac{16*5}{9}$$ = $$\frac{80}{9}$$ = 8.888 (9x9 = 81, 80 is little less than 81, therefore maximum of 8 monkeys can use 16 Liters of water)
Therefore Maximum number of monkeys who can use 16 Liters of water = 8

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Re: In a certain zoo, 9L of water can sustain 5 monkeys   [#permalink] 20 May 2017, 03:28
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