2012 AMC 10A Problem 1

Problem 1 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

Cagney can make

60 \div 20 = 3

cupcakes per minute, and Lacey can make

60 \div 30 = 2.

5

minutes, they can make

5(2 + 3) = 5 \cdot 5 = 25.

Thus, D is the correct answer.

Concepts: rate · unit conversion

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