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During a one-year study, biologists observed the number of fish in a ce

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During a one-year study, biologists observed the number of fish in a ce  [#permalink]

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New post 15 Jul 2018, 08:54
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78% (01:33) correct 22% (01:41) wrong based on 46 sessions

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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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Re: During a one-year study, biologists observed the number of fish in a ce  [#permalink]

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New post 15 Jul 2018, 13:13
2003 --> 300 fish, 15% catfish. 300*0.15=45
2004 --> 400 fish, 10% catfish, 400*0.1=40

Decrease is obvious, lets calculate the % change
45-40=5 \(\frac{5}{45}\)*100~11%

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Re: During a one-year study, biologists observed the number of fish in a ce  [#permalink]

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New post 15 Jul 2018, 18:16
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Bunuel wrote:
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%


Change in catfish 15% of 300 -10% of 400=\(300*\frac{15}{100}-400*\frac{10}{100}=45-40=5\)

Now all answer choices are related to 5% which actually means 5 in 100.
But here the decrease of 5 has been over 45, which is greater than 5 in 100.
Thus decreased by more than 5%

A
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Re: During a one-year study, biologists observed the number of fish in a ce &nbs [#permalink] 15 Jul 2018, 18:16
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