2011 AMC 12A 第 5 题

Question

去年夏天，Town Lake 上生活的鸟中

30\%

是鹅，

25\%

是天鹅，

10\%

是鹭，

35\%

是鸭。在不是天鹅的鸟中，鹅占百分之几？

Last summer

30\%

of the birds living on Town Lake were geese,

25\%

were swans,

10\%

were herons, and

35\%

were ducks. What percent of the birds that were not swans were geese?

20

30

40

50

60

不是天鹅的鸟占总数的

75\%

The non-swan birds make up

75\%

of the total

把

\dfrac{30}{75}

化成百分数

Compute

\dfrac{30}{75}

as a percent

不是天鹅的鸟占总数的

100\% - 25\% = 75\%

，而鹅占总数的

30\%

。所求比例为

\dfrac{30}{75} = \dfrac{2}{5} = 40\%\text{。}

因此，正确答案是 C。

The birds that are not swans make up

100\% - 25\% = 75\%

of the total, and geese are

30\%

of the total. The requested fraction is

\dfrac{30}{75} = \dfrac{2}{5} = 40\%.

Thus, the correct answer is C.

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