Difference between revisions of "2003 AMC 10A Problems/Problem 4"

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(Redirected page to 2003 AMC 12A Problems/Problem 4)
 
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== Problem ==
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#REDIRECT[[2003 AMC 12A Problems/Problem 4]]
It takes Mary <math>30</math> minutes to walk uphill <math>1</math> km from her home to school, but it takes her only <math>10</math> minutes to walk from school to her home along the same route. What is her average speed, in km/hr, for the round trip?
 
 
 
<math> \mathrm{(A) \ } 3\qquad \mathrm{(B) \ } 3.125\qquad \mathrm{(C) \ } 3.5\qquad \mathrm{(D) \ } 4\qquad \mathrm{(E) \ } 4.5 </math>
 
 
 
== Solution ==
 
Since she walked <math>1</math> km to school and <math>1</math> km back home, her total distance is <math>1+1=2</math> km.
 
 
 
Since she spent <math>30</math> minutes walking to school and <math>10</math> minutes walking back home, her total time is <math>30+10=40</math> minutes = <math>\frac{40}{60}=\frac{2}{3}</math> hours.
 
 
 
Therefore her average speed in km/hr is <math>\frac{2}{\frac{2}{3}}=3 \Rightarrow A</math>
 
 
 
== See Also ==
 
{{AMC10 box|year=2003|ab=A|num-b=3|num-a=5}}
 
 
 
[[Category:Introductory Algebra Problems]]
 

Latest revision as of 17:23, 29 July 2011