Bunuel wrote:
David drove to work at an average (arithmetic mean) speed of 45 miles per hour. After work, David drove home at an average speed of 60 miles per hour. If David spent a total of 2 hours commuting to and from work, how many miles does David drive to work?
A. 48
B. 256/5
C. 360/7
D. 105/2
E. 160/3
Note:- Travelling distance(To & Fro journeys) is equal.
Distance travelled from home to work=Distance travelled from work to home.
Given, \(V_{hw}=45mph\), \(V_{wh}=60mph\), and total travel time,T=2 hrs
Average speed(h-w-h)=Total distance/Total Time
Or, Total distance(h-w-h)=\(v_{avg}*T=\frac{2*V_{hw}*V_{wh}}{V_{hw}+V_{wh}}*T\) =\(\frac{2*45*60*2}{45+60}\)=\(\frac{720}{7}\)
Or, 2*distance from home to work=\(\frac{720}{7}\)
Or, distance from home to work=\(\frac{360}{7}\)
Ans. (C)
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Regards,
PKN
Rise above the storm, you will find the sunshine