2004 AMC 10A Problems/Problem 19

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Problem

A white cylindrical silo has a diameter of 30 feet and a height of 80 feet. A red stripe with a horizontal width of 3 feet is painted on the silo, as shown, making two complete revolutions around it. What is the area of the stripe in square feet?

$\mathrm{(A) \ } 120 \qquad \mathrm{(B) \ } 180 \qquad \mathrm{(C) \ } 240 \qquad \mathrm{(D) \ } 360 \qquad \mathrm{(E) \ } 480$

Solution

The cylinder can be "unwrapped" into a rectangle, and we see that the stripe is a parallelogram with base 3 and height 80. $3\cdot 80=240\Rightarrow \boxed{\mathrm{(C) \ }}$

2004 AMC 10A (Problems)
Preceded by Problem 18	Followed by Problem 20
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2004 AMC 10A Problems/Problem 19

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Problem

Solution

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