Art of Problem Solving

1952 AHSME Problems/Problem 27: Difference between revisions

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== Problem==
The ratio of the perimeter of an equilateral triangle having an altitude equal to the radius of a circle, to the perimeter of an equilateral triangle inscribed in the circle is:


<math> \textbf{(A)}\ 1:2\qquad\textbf{(B)}\ 1:3\qquad\textbf{(C)}\ 1:\sqrt3\qquad\textbf{(D)}\ \sqrt3:2 \qquad\textbf{(E)}\ 2:3</math>
==Solution==
If the radius of the circle is <math>r</math>, then the perimeter of the first triangle is <math>3\left(\frac{2r}{\sqrt3}\right)=2r\sqrt3</math>, and the perimeter of the second is <math>3r\sqrt3</math>. So the ratio is <math>\boxed{\frac23{\textbf{ (E)}}}</math>.
==See also==
{{AHSME 50p box|year=1952|num-b=26|num-a=28}}
{{MAA Notice}}

Latest revision as of 20:13, 19 April 2014

Problem

The ratio of the perimeter of an equilateral triangle having an altitude equal to the radius of a circle, to the perimeter of an equilateral triangle inscribed in the circle is:

$\textbf{(A)}\ 1:2\qquad\textbf{(B)}\ 1:3\qquad\textbf{(C)}\ 1:\sqrt3\qquad\textbf{(D)}\ \sqrt3:2 \qquad\textbf{(E)}\ 2:3$

Solution

If the radius of the circle is $r$, then the perimeter of the first triangle is $3\left(\frac{2r}{\sqrt3}\right)=2r\sqrt3$, and the perimeter of the second is $3r\sqrt3$. So the ratio is $\boxed{\frac23{\textbf{ (E)}}}$.

See also

1952 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 26
Followed by
Problem 28
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