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When frightened, a certain puffer fish rapidly expands by 70%. Shortly

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When frightened, a certain puffer fish rapidly expands by 70%. Shortly [#permalink]

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New post 13 Feb 2017, 02:11
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When frightened, a certain puffer fish rapidly expands by 70%. Shortly thereafter, the fish contracts by 70%. By what approximate percentage does the puffer fish then need to expand again in order to return to its initial size?

A. 0%
B. 20%
C. 50%
D. 70%
E. 100%
[Reveal] Spoiler: OA

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When frightened, a certain puffer fish rapidly expands by 70%. Shortly [#permalink]

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New post 13 Feb 2017, 03:00
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Bunuel wrote:
When frightened, a certain puffer fish rapidly expands by 70%. Shortly thereafter, the fish contracts by 70%. By what approximate percentage does the puffer fish then need to expand again in order to return to its initial size?

A. 0%
B. 20%
C. 50%
D. 70%
E. 100%


let x be the original size
x expands by 70% => 1.7*x then contracts by 70% => 1.7*0.3*x = 0.51*x
To expand again in order to return to its initial size the puffer needs almost 50% to get back to original size x
So it needs to expand by 100%.

Hence Option E is correct.
Hit Kudos if you liked it 8-).

Last edited by 0akshay0 on 13 Feb 2017, 20:11, edited 1 time in total.
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Re: When frightened, a certain puffer fish rapidly expands by 70%. Shortly [#permalink]

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New post 13 Feb 2017, 06:05
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Bunuel wrote:
When frightened, a certain puffer fish rapidly expands by 70%. Shortly thereafter, the fish contracts by 70%. By what approximate percentage does the puffer fish then need to expand again in order to return to its initial size?

A. 0%
B. 20%
C. 50%
D. 70%
E. 100%


Assuming the initial size of a puffer to be 100.

After expansion by 70%, new size is 170.

After contraction by 70%, the new size is 51. (30% of 170)

Now the puffer has to almost double itself to gain its original size of 100. So the size has to increase by 100%.

Answer E

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When frightened, a certain puffer fish rapidly expands by 70%. Shortly [#permalink]

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New post 17 Feb 2017, 03:36
Answer : [E]

Net change = +70 -70 (+)(-) (70*70) / (100* 100) = 49%

Resultant size = 51%

Required growth percent = 49 / 51 =100 %
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Re: When frightened, a certain puffer fish rapidly expands by 70%. Shortly [#permalink]

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New post 23 Feb 2017, 09:29
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Bunuel wrote:
When frightened, a certain puffer fish rapidly expands by 70%. Shortly thereafter, the fish contracts by 70%. By what approximate percentage does the puffer fish then need to expand again in order to return to its initial size?

A. 0%
B. 20%
C. 50%
D. 70%
E. 100%


We can let x = the initial size of the fish. Since it expands by 70% and then contracts by 70%, we can create the following expression:

x(1.7)(0.3) = x(0.51)

To return to its original size, the fish needs to increase by roughly 100%, since 2(0.51x) = 1.02x.

Answer: E
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Re: When frightened, a certain puffer fish rapidly expands by 70%. Shortly   [#permalink] 23 Feb 2017, 09:29
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