Difference between revisions of "1966 AHSME Problems/Problem 34"

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(Solution)
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== Solution ==
 
== Solution ==
<math>\fbox{B}</math>
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<math>The circumference of the wheel is </math>\frac{11}{5280}<math> miles. Let the time for the rotation in seconds be </math>t<math>. So </math>rt=\frac{11}{5280}*3600<math>. We also know reducing the time by </math>\frac{1}{4}<math> of a second makes </math>r<math> increase by </math>5<math>. So </math>(r+5)(t-\frac{1}{4})=\frac{11}{5280}*3600<math>. Solving for </math>r<math> we get </math>r=10<math>. So our answer is </math>(B)<math> </math>10<math>.</math>
  
 
== See also ==
 
== See also ==

Revision as of 23:05, 12 September 2015

Problem

Let $r$ be the speed in miles per hour at which a wheel, $11$ feet in circumference, travels. If the time for a complete rotation of the wheel is shortened by $\frac{1}{4}$ of a second, the speed $r$ is increased by $5$ miles per hour. Then $r$ is:

$\text{(A) } 9 \quad \text{(B) } 10 \quad \text{(C) } 10\frac{1}{2} \quad \text{(D) } 11 \quad \text{(E) } 12$

Solution

$The circumference of the wheel is$\frac{11}{5280}$miles. Let the time for the rotation in seconds be$t$. So$rt=\frac{11}{5280}*3600$. We also know reducing the time by$\frac{1}{4}$of a second makes$r$increase by$5$. So$(r+5)(t-\frac{1}{4})=\frac{11}{5280}*3600$. Solving for$r$we get$r=10$. So our answer is$(B)$$ (Error compiling LaTeX. Unknown error_msg)10$.$

See also

1966 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 33
Followed by
Problem 35
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