AMC8 1997

AMC8 1997 · Q13

AMC8 1997 · Q13. It mainly tests Ratios & proportions, Averages (mean).

Three bags of jelly beans contain 26, 28, and 30 beans. The ratios of yellow beans to all beans in each of these bags are 50%, 25%, and 20%, respectively. All three bags of candy are dumped into one bowl. Which of the following is closest to the ratio of yellow jelly beans to all beans in the bowl?

三个果冻豆袋子分别含 26、28 和 30 颗豆子。各袋中黄色豆子与总豆子的比例分别为 50%、25% 和 20%。将三个袋子全部倒入一个碗中。碗中黄色果冻豆与总豆子的比例最接近以下哪一项？

(A) 31% 31%

(B) 32% 32%

(D) 35% 35%

(E) 95% 95%

Answer

Correct choice: (A)

正确答案：（A）

Solution

Answer (A): There is a total of $26+28+30=84$ jelly beans: $50\%$ of $26=13$ $25\%$ of $28=7$ $20\%$ of $30=\underline{6}$ $\underline{26}$ $\dfrac{26}{84}=0.3095\approx 31\%$

答案（A）：一共有 $26+28+30=84$ 颗果冻豆： $26$ 的 $50\%=13$ $28$ 的 $25\%=7$ $30$ 的 $20\%=\underline{6}$ $\underline{26}$ $\dfrac{26}{84}=0.3095\approx 31\%$

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