Difference between revisions of "2003 AMC 10A Problems/Problem 17"
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== Problem == | == Problem == | ||
− | The number of inches in the perimeter of an equilateral triangle equals the number of square inches in the area of its circumscribed circle. What is the radius, in inches, of the circle? | + | <!-- don't remove the following tag, for PoTW on the Wiki front page--><onlyinclude>The number of inches in the perimeter of an equilateral triangle equals the number of square inches in the area of its circumscribed circle. What is the radius, in inches, of the circle? <!-- don't remove the following tag, for PoTW on the Wiki front page--></onlyinclude> |
<math> \mathrm{(A) \ } \frac{3\sqrt{2}}{\pi}\qquad \mathrm{(B) \ } \frac{3\sqrt{3}}{\pi}\qquad \mathrm{(C) \ } \sqrt{3}\qquad \mathrm{(D) \ } \frac{6}{\pi}\qquad \mathrm{(E) \ } \sqrt{3}\pi </math> | <math> \mathrm{(A) \ } \frac{3\sqrt{2}}{\pi}\qquad \mathrm{(B) \ } \frac{3\sqrt{3}}{\pi}\qquad \mathrm{(C) \ } \sqrt{3}\qquad \mathrm{(D) \ } \frac{6}{\pi}\qquad \mathrm{(E) \ } \sqrt{3}\pi </math> | ||
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Let <math>s</math> be the length of a side of the equilateral triangle and let <math>r</math> be the radius of the circle. | Let <math>s</math> be the length of a side of the equilateral triangle and let <math>r</math> be the radius of the circle. | ||
− | In a circle with a radius <math>r</math> the side of an inscribed equilateral triangle is <math>r\sqrt{3}</math>. | + | In a circle with a radius <math>r</math>, the side of an inscribed equilateral triangle is <math>r\sqrt{3}</math>. |
So <math>s=r\sqrt{3}</math>. | So <math>s=r\sqrt{3}</math>. | ||
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<math>\pi r=3\sqrt{3}</math> | <math>\pi r=3\sqrt{3}</math> | ||
− | <math>r=\frac{3\sqrt{3}}{\pi} \Rightarrow B</math> | + | <math>r=\frac{3\sqrt{3}}{\pi} \Rightarrow\boxed{\mathrm{(B)}\ \frac{3\sqrt{3}}{\pi}}</math> |
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+ | ==Video Solution== | ||
+ | https://youtu.be/El9eQJmDO78 | ||
+ | |||
+ | ~savannahsolver | ||
== See Also == | == See Also == | ||
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[[Category:Introductory Geometry Problems]] | [[Category:Introductory Geometry Problems]] | ||
+ | {{MAA Notice}} |
Revision as of 12:23, 7 February 2022
Contents
Problem
The number of inches in the perimeter of an equilateral triangle equals the number of square inches in the area of its circumscribed circle. What is the radius, in inches, of the circle?
Solution
Let be the length of a side of the equilateral triangle and let be the radius of the circle.
In a circle with a radius , the side of an inscribed equilateral triangle is .
So .
The perimeter of the triangle is
The area of the circle is
So:
Video Solution
~savannahsolver
See Also
2003 AMC 10A (Problems • Answer Key • Resources) | ||
Preceded by Problem 16 |
Followed by Problem 18 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AMC 10 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.