2007 AMC 12A Problem 4

Problem 4 of 25EasierAlgebra

Kate rode her bicycle for

30

minutes at a speed of

16

mph, then walked for

90

minutes at a speed of

4

mph. What was her overall average speed in miles per hour?

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Solution

Kate rode for

\tfrac12

hour at

16

mph, covering

8

miles. She walked for

\tfrac32

hours at

4

mph, covering

6

miles. She covered

14

miles in

2

hours, so her average speed was

7

mph. Thus, the correct answer is A.

Concepts: distance rate and time

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