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During a one-year study, biologists observed the number of ﬁ

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During a one-year study, biologists observed the number of ﬁ [#permalink]  30 Jan 2016, 09:06
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Question Stats:

86% (00:59) correct 13% (01:23) wrong based on 22 sessions
During a one-year study, biologists observed the number of ﬁsh in a certain pond as well as the percent of the ﬁsh that were catﬁsh. At the beginning of the year, there were 300 ﬁsh in the pond, of which 15 percent were catﬁsh; and at the end of the year, there were 400 ﬁsh in the pond, of which 10 percent were catﬁsh. From the beginning of the year to the end of the year, the number of catﬁsh in the pond

 A decreased by more than 5%
 B decreased by 5%
 C did not change
 D increased by 5%
 E increased by more than 5%

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Question: 13
Page: 468
Difficulty: medium
[Reveal] Spoiler: OA

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Joined: 18 Apr 2015
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Kudos [?]: 1275 [0], given: 6017

Re: During a one-year study, biologists observed the number of ﬁ [#permalink]  30 Jan 2016, 09:08
Expert's post
Solution

$$300*0.15=45$$

$$400*0.1=40$$

% decrease is actually 5

$$\frac{5}{45}=11%$$

The answer is $$A$$
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Re: During a one-year study, biologists observed the number of ﬁ [#permalink]  26 Nov 2018, 18:45
i got the same results up until 5 over 45. Can you please explain that and why the answer is not "decreased by 5%"?
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Re: During a one-year study, biologists observed the number of ﬁ [#permalink]  26 Nov 2018, 23:49
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early during the year catfish were 15% of 300 which is 45
while later during that year it was 10% of 400 which is 40
Hence the decrease is 5 and as a % it will be 5/45*100 = 11.11% from the start of the year.
Re: During a one-year study, biologists observed the number of ﬁ   [#permalink] 26 Nov 2018, 23:49
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