2009 AMC 10B Problem 5

Attempt Problem 5 of the 2009 AMC 10B 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 2009 AMC 10B solutions, or check the answer key.

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

5.

Twenty percent less than 6060 is one-third more than what number?
1616
3030
3232
3636
4848
Answer: D
Concepts:percentagelinear equation
Small hint:
Twenty percent less than 6060 is 45⋅60\dfrac45\cdot60
Big hint:
One-third more than nn is 43n\dfrac43 n
Solution:
Twenty percent less than 6060 is 45⋅60=48.\dfrac45\cdot60=48.
If nn is the unknown number, one-third more than nn is 43n,\dfrac43 n, so 43n=48 \dfrac43 n=48 n=36. n=36.
Thus, the correct answer is D.
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