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?
A. 20
B. $33\frac{1}{3}$
C. 38
D. 45
E. 54

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Worked solution

1. 2019 AMC 8 官方解析

Gilda有一包玻璃球 . 她给她的朋友Pedro20% . 而后她又拿出剩下的10%给另一个朋友Ebony . 最后在所剩的之中拿出了25%给她哥哥 Jimmy . 至此她包里所剩的玻璃球是最初的百分之多少？

$(1 - 20\%) \times (1 - 10\%) \times (1 - 25\%) = \frac{4}{5} \times \frac{9}{10} \times \frac{3}{4} = \frac{27}{50} = 54\%$ .

Answer

E. 54

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