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

游客2024-01-12  27

问题 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

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

答案 A

解析 The answer choices indicate that the question is asking about the percent change in the number of catfish. The number of catfish in the pond at the beginning of the year was 15% of 300, or(0.15)(300), which is 45. The number of catfish in the pond at the end of the year was 10% of 400, or(0.10)(400), which is 40. Thus, the number of catfish decreased by 5.
    The percent by which the number of catfish decreased from the beginning of the year to the end of the year is

Thus, the number of catfish decreased by about 11%. This is a decrease of more than 5%, so the correct answer is Choice A.
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