AMC10 2009 A

AMC10 2009 A · Q18

AMC10 2009 A · Q18. It mainly tests Percent, Probability (basic).

At Jefferson Summer Camp, 60% of the children play soccer, 30% of the children swim, and 40% of the soccer players swim. To the nearest whole percent, what percent of the non-swimmers play soccer?

在杰斐逊夏令营，60%的孩子踢足球，30%的孩子游泳，且40%的踢足球的孩子游泳。不游泳的孩子中有大约百分之多少踢足球？（结果四舍五入到最接近的整百分比）

(A) 30% 30%

(B) 40% 40%

(D) 51% 51%

(E) 70% 70%

Answer

Correct choice: (D)

正确答案：（D）

Solution

Answer (D): For every 100 children, 60 are soccer players and 40 are non-soccer players. Of the 60 soccer players, 40% or $60 \times \frac{40}{100} = 24$ are also swimmers, so 36 are non-swimmers. Of the 100 children, 30 are swimmers and 70 are non-swimmers. The fraction of non-swimmers who play soccer is $\frac{36}{70} \approx .51$, or 51%.

答案（D）：每 100 个孩子中，60 个踢足球，40 个不踢足球。在这 60 个踢足球的孩子中，40%（即 $60 \times \frac{40}{100} = 24$）同时也是游泳者，因此有 36 个不是游泳者。在这 100 个孩子中，30 个是游泳者，70 个不是游泳者。不游泳但踢足球的比例是 $\frac{36}{70} \approx .51$，即 51%。

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