2012 AMC 12A Problem 2

Problem 2 of 25EasierAlgebra

Cagney can frost a cupcake every

20

seconds and Lacey can frost a cupcake every

30

seconds. Working together, how many cupcakes can they frost in

5

minutes?

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Solution

5

minutes there are

300

seconds. Cagney frosts

\dfrac{300}{20} = 15

cupcakes and Lacey frosts

\dfrac{300}{30} = 10

cupcakes. Together they frost

15 + 10 = 25

cupcakes. Thus, the correct answer is D.

Concepts: rate · unit conversion

Problem text and solution from the LIVE past-contest archive. See also the AoPS wiki page for community solutions.