Question

去年夏天，Town Lake 上的鸟中 $30 \%$ 是鹅， $25 \%$ 是天鹅， $10 \%$ 是鹭， $35 \%$ 是鸭。不是天鹅的鸟中，百分之多少是鹅？

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?

$20$

$30$

$40$

$50$

$60$

答案：C

知识点：百分数比与比例

难度评级：870

解答：

不妨设共有 $100$ 只鸟，则不是天鹅的有 $75$ 只，其中三十只是鹅。 $\dfrac{30}{75} \cdot 100 = 40 \%.$

所以正确答案是 C。

WLOG, let there be $100$ birds. Then $75$ birds are not swans. The desired percentage is then $\dfrac{30}{75} \cdot 100 = 40 \%.$

Thus, C is the correct answer.

2011 AMC 10A 第 8 题

答案：C

难度评级：870

解答：

其他年份的第 8 题