Difference between revisions of "2017 AMC 10B Problems/Problem 2"

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==Solution==
 
==Solution==
  
If Sofia ran the first <math>100</math> meters of each lap at <math>4</math> meters per second, and the remaining <math>300</math> meters of each lap at <math>5</math> meters per second, then she took <math>25+60=85</math> seconds for each lap. Multiply this by <math>5</math> (because she ran <math>5</math> laps) to get <math>425</math> seconds, or <math>7</math> minutes and <math>5</math> seconds, which matches the answer choice <math>\boxed{\textbf{(C)} }</math>
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If Sofia ran the first <math>100</math> meters of each lap at <math>4</math> meters per second and the remaining <math>300</math> meters of each lap at <math>5</math> meters per second, then she took <math>\frac{100}{4}+\frac{300}{5}=25+60=85</math> seconds for each lap. Because she ran <math>5</math> laps, she took a total of <math>5 \cdot 85=425</math> seconds, or <math>7</math> minutes and <math>5</math> seconds. The answer is <math>\boxed{\textbf{(C)} }</math>.
  
 
==See Also==
 
==See Also==
 
{{AMC10 box|year=2017|ab=B|num-b=1|num-a=3}}
 
{{AMC10 box|year=2017|ab=B|num-b=1|num-a=3}}
 
{{MAA Notice}}
 
{{MAA Notice}}

Revision as of 12:47, 16 February 2017

Problem

Sofia ran $5$ laps around the $400$-meter track at her school. For each lap, she ran the first $100$ meters at an average speed of $4$ meters per second and the remaining $300$ meters at an average speed of $5$ meters per second. How much time did Sofia take running the $5$ laps?

$\textbf{(A)}\ 5$ minutes and $35$ seconds $\qquad\textbf{(B)}\ 6$ minutes and $40$ seconds $\qquad\textbf{(C)}\ 7$ minutes and $5$ seconds $\qquad\textbf{(D)}\ 7$ minutes and $25$ seconds $\qquad\textbf{(E)}\ 8$ minutes and $10$ seconds

Solution

If Sofia ran the first $100$ meters of each lap at $4$ meters per second and the remaining $300$ meters of each lap at $5$ meters per second, then she took $\frac{100}{4}+\frac{300}{5}=25+60=85$ seconds for each lap. Because she ran $5$ laps, she took a total of $5 \cdot 85=425$ seconds, or $7$ minutes and $5$ seconds. The answer is $\boxed{\textbf{(C)} }$.

See Also

2017 AMC 10B (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
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

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