2019 AMC 8 Problem 8

Below is the video solution and professionally curated solution for Problem 8 of the 2019 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2019 AMC 8 solutions, or check the answer key.

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Concepts:percentage

Difficulty rating: 960

8.

Gilda has a bag of marbles. She gives 20%20\% of them to her friend Pedro. Then Gilda gives 10%10\% of what is left to another friend, Ebony. Finally, Gilda gives 25%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?

2020

331333\dfrac{1}{3}

3838

4545

5454

Video solution:
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Written solution:

Assume that Gilda starts off with 100100 marbles. After giving 2020 marbles to Pedro, she has 10020=80100 - 20 = 80 marbles left.

She then gives 80×.1=880 \times .1 = 8 marbles to Ebony, with her having 808=7280 - 8 = 72 marbles left.

Finally, Gilda gives 72×.25=1872 \times .25 = 18 marbles to Jimmy. She has a total of 7218=5472 - 18 = 54 marbles left, which is 54%54\% of her original total.

Thus, the correct answer is E.

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