Difference between revisions of "1953 AHSME Problems/Problem 11"
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| − | A running track is the ring formed by two concentric circles. It is <math> 10</math> feet wide. The circumference of the two circles differ by about | + | A running track is the ring formed by two concentric circles. It is <math>10</math> feet wide. The circumference of the two circles differ by about: |
| + | <math>\textbf{(A)}\ 10\text{ feet} \qquad | ||
| + | \textbf{(B)}\ 30\text{ feet} \qquad | ||
| + | \textbf{(C)}\ 60\text{ feet} \qquad | ||
| + | \textbf{(D)}\ 100\text{ feet}\\ \textbf{(E)}\ \text{none of these} </math> | ||
== Solution == | == Solution == | ||
Revision as of 11:19, 22 April 2020
A running track is the ring formed by two concentric circles. It is 
feet wide. The circumference of the two circles differ by about:
Solution
Call the radius of the outer circle 
and that of the inner circle 
. The width of the track is 
. The circumference of a circle is 
times the radius, so the difference in circumferences is 
feet. If we divide each side by , we get 
feet.
See Also
| 1953 AHSC (Problems • Answer Key • Resources) | ||
| Preceded by Problem 10 |
Followed by Problem 12 | |
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| All AHSME Problems and Solutions | ||
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. 
