Thread: Ratios of Areas Help
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Old June 24th, 2009, 04:15 PM
yeongil yeongil is offline
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Originally Posted by dvh9 View Post
2) Two similar triangles have corresponding sides with lengths 3 and 9. If the area of the first triangle is 12, what is the area of the second triangle? (Answer = 108)
The area of a triangle is A = \frac{1}{2}bh. In the first triangle, the base is 3 and the area is 12:

\begin{aligned}12 &= \frac{1}{2}(3)h \\h &= 8\end{aligned}

The base of the 2nd triangle is triple the base of the first (3 x 3 = 9), so we triple the height as well (8 x 3 = 24) and find the area:

\begin{aligned}A &= \frac{1}{2}(9)(24) \\&= 108\end{aligned}


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