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

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== Solution ==
 
== Solution ==
<math>\fbox{B}</math>
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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>.
  
 
== See also ==
 
== See also ==
 
{{AHSME box|year=1966|num-b=33|num-a=35}}   
 
{{AHSME box|year=1966|num-b=33|num-a=35}}   
  
[[Category:Intermediate Algebra Problems]]
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[[Category:Introductory Algebra Problems]]
 
{{MAA Notice}}
 
{{MAA Notice}}

Latest revision as of 18:59, 29 May 2024

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 $(B)$ $10$.

See also

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