AMC10 2011 A

AMC10 2011 A · Q8

AMC10 2011 A · Q8. It mainly tests Percent.

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?

去年夏天，镇湖上35%的鸟是鹅，25%是天鹅，10%是鹭鸶，35%是鸭子。非天鹅的鸟中，有多少百分比是鹅？

(A) 20 20

(B) 30 30

(D) 50 50

(E) 60 60

Answer

Correct choice: (C)

正确答案：（C）

Solution

Because 75% of the birds were not swans and 30% of the birds were geese, it follows that $\frac{30}{75} \cdot 100\% = 40\%$ of the birds that were not swans were geese.

因为75%的鸟不是天鹅，30%的鸟是鹅，因此$\frac{30}{75} \cdot 100\% = 40\%$的非天鹅鸟是鹅。

Topics

AR.003 Percent