2009 AMC 10B Problem 3

Below is the professionally curated solution for Problem 3 of the 2009 AMC 10B, 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.

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Concepts:ratio and proportion rate

Difficulty rating: 870

Paula the painter had just enough paint for $30$ identically sized rooms. Unfortunately, on the way to work, three cans of paint fell off her truck, so she had only enough paint for $25$ rooms. How many cans of paint did she use for the $25$ rooms?

$10$

$12$

$15$

$18$

$25$

Solution:

The lost $3$ cans would have painted $30-25=5$ rooms, so each room takes $\dfrac35$ of a can.

For $25$ rooms she used $\dfrac35\cdot25=15$ cans.

Thus, the correct answer is C.

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Problem 3 in Other Years

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