2010 AMC 10A Problem 1

Problem 1 of 25EasierAlgebra

Mary’s top book shelf holds five books with the following widths, in centimeters:

6,

\dfrac{1}{2},

1,

2.5,

and

10.

What is the average book width, in centimeters?

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Solution

Adding the five widths gives

6+\dfrac12+1+2.5+10=20.

The average is

20\div5=4.

Thus, D is the correct answer.

Concepts: mean · decimal

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