1964 AHSME Problems/Problem 10

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Problem

Given a square side of length $s$. On a diagonal as base a triangle with three unequal sides is constructed so that its area equals that of the square. The length of the altitude drawn to the base is:

$\textbf{(A)}\ s\sqrt{2} \qquad \textbf{(B)}\ s/\sqrt{2} \qquad \textbf{(C)}\ 2s \qquad \textbf{(D)}\ 2\sqrt{s} \qquad \textbf{(E)}\ 2/\sqrt{s}$

Solution

The area of the square is $s^2$. The diagonal of a square with side $s$ bisects the square into two $45-45-90$ right triangles, so the diagonal has length $s\sqrt{2}$.

The area of the triangle is $\frac{1}{2}bh$. The base $b$ of the triangle is the diagonal of the square, which is $b = s\sqrt{2}$. If the area of the triangle is equal to the area of the square, we have:

$s^2 = \frac{1}{2}bh$

$s^2 = \frac{1}{2}s\sqrt{2}\cdot h$

$s = \frac{\sqrt{2}}{2}h$

$h = \frac{2}{\sqrt{2}}s$

$h = s\sqrt{2}$

This is option $\boxed{\textbf{(A)}}$

See Also

1964 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 9
Followed by
Problem 11
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