2000 AMC 8 Problems/Problem 16

Problem

In order for Mateen to walk a kilometer (1000m) in his rectangular backyard, he must walk the length 25 times or walk its perimeter 10 times. What is the area of Mateen's backyard in square meters?

$\text{(A)}\ 40 \qquad \text{(B)}\ 200 \qquad \text{(C)}\ 400 \qquad \text{(D)}\ 500 \qquad \text{(E)}\ 1000$

Solution

The length $L$ of the rectangle is $\frac{1000}{25}=40$ meters. The perimeter $P$ is $\frac{1000}{10}=100$ meters. Since $P_{rect} = 2L + 2W$ , we plug values in to get:

$100 = 2\cdot 40 + 2W$

$100 = 80 + 2W$

$2W = 20$

$W = 10$ meters

Since $A_{rect} = LW$ , the area is $40\cdot 10=400$ square meters or $\boxed{C}$ .

2000 AMC 8 (Problems • Answer Key • Resources)
Preceded by Problem 15	Followed by Problem 17
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2000 AMC 8 Problems/Problem 16

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