2010 AMC 10A Problem 3

Attempt Problem 3 of the 2010 AMC 10A below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2010 AMC 10A solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

3.

Tyrone had 9797 marbles and Eric had 1111 marbles. Tyrone then gave some of his marbles to Eric so that Tyrone ended with twice as many marbles as Eric. How many marbles did Tyrone give to Eric?
33
1313
1818
2525
2929
Answer: D
Concepts:linear equationratio and proportion
Small hint:
The total number of marbles stays fixed
Big hint:
The final amounts are in the ratio 2:12:1
Solution:
Let xx be the number of marbles that Eric ends up with. Then Tyrone ends up with 2x.2x.
The total number of marbles is 97+11=108,97 + 11 = 108, so 3x=108 3x = 108 x=36.x = 36.
Then, Tyrone ends up with 36⋅2=7236 \cdot 2 = 72 marbles. This means he has to give away 97−72=2597 - 72 = 25 marbles.
Thus, D is the correct answer.
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