2007 AMC 12A Problems/Problem 4

Problem

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?

$\displaystyle \mathrm{(A)}\ 7\qquad \mathrm{(B)}\ 9\qquad \mathrm{(C)}\ 10\qquad \mathrm{(D)}\ 12\qquad \mathrm{(E)}\ 14$

Solution

$16 \cdot \frac{30}{60}+4\cdot\frac{90}{60}=14$
$\displaystyle \frac{14}2=7$

2007 AMC 12A (Problems • Answer Key • Resources)
Preceded by Problem 3	Followed by Problem 5
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2007 AMC 12A Problems/Problem 4

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