AMC8 2019

AMC8 2019 · Q8

AMC8 2019 · Q8. It mainly tests Fractions, Percent.

Gilda has a bag of marbles. She gives $20\%$ of them to her friend Pedro. Then Gilda gives $10\%$ of what is left to another friend, Ebony. Finally, Gilda gives $25\%$ of what is now left in the bag to her brother Jimmy. What percentage of her original bag of marbles does Gilda have left for herself?

Gilda 有一个弹珠袋。她将其中 $20\%$ 给了朋友 Pedro。然后将剩下的 $10\%$ 给了另一个朋友 Ebony。最后将现在袋中剩下的 $25\%$ 给了弟弟 Jimmy。Gilda 自己剩下原来弹珠袋的百分之多少？

(A) 20 20

(B) 33\frac{1}{3} 33\frac{1}{3}

(D) 45 45

(E) 54 54

Answer

Correct choice: (E)

正确答案：（E）

Solution

After Gilda gives $20$% of the marbles to Pedro, she has $80$% of the marbles left. If she then gives $10$% of what's left to Ebony, she has $(0.8*0.9)$ = $72$% of what she had at the beginning. Finally, she gives $25$% of what's left to her brother, so she has $(0.75*0.72)$ $\boxed{\textbf{(E)}\ 54}$ of what she had in the beginning left.

给了 Pedro $20\%$ 后，剩下 $80\%$。然后给了 Ebony 剩下部分的 $10\%$，剩下 $(0.8\times0.9)=72\%$。最后给了 Jimmy 剩下部分的 $25\%$，所以剩下 $(0.75\times0.72)=\boxed{\textbf{(E)}\ 54}$。

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