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Joined: 16 May 2014
Posts: 592
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GRE 1: Q165 V161
GRE Math Challenge #7-David drove to work at an average
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15 Sep 2014, 22:03
15 Sep 2014, 22:03
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Question Stats:
64% (01:32) correct
35% (01:27) wrong based on 178 sessions
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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)\(\frac{256}{5}\)
C)\(\frac{360}{7}\)
D)\(\frac{105}{2}\)
E)\(\frac{160}{3}\)
A)48
B)\(\frac{256}{5}\)
C)\(\frac{360}{7}\)
D)\(\frac{105}{2}\)
E)\(\frac{160}{3}\)
Re: GRE Math Challenge #7-David drove to work at an average
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02 Feb 2018, 08:55
02 Feb 2018, 08:55
3
The total distance going from home to work = total distance going from work to home
In the 1st case David drove @ an average speed of 45 miles per hour so distance \(d = 45 h1\)where \(h1\)is the time taken to complete the distance
In the 2nd case David drove @ an average speed of 60 miles per hour so distance \(d = 60 h2\)where \(h2\)is the time taken to complete the return journey from work to home
Given,
\(h1 + h2 = 2\)
we get,\(h1 = 2 - h2\)
Since distance is equal for going to work from home and coming back to home from work
\(45h1 = 60h2\)
hence, \(45(2 - h2) = 60 h2\)
solve for h2 it should equal\(\frac{90}{105}\)
Solve for D by replacing value of h2 in the eqn \(60* h2\)
\(d =\frac{360}{7}\)
(C)
In the 1st case David drove @ an average speed of 45 miles per hour so distance \(d = 45 h1\)where \(h1\)is the time taken to complete the distance
In the 2nd case David drove @ an average speed of 60 miles per hour so distance \(d = 60 h2\)where \(h2\)is the time taken to complete the return journey from work to home
Given,
\(h1 + h2 = 2\)
we get,\(h1 = 2 - h2\)
Since distance is equal for going to work from home and coming back to home from work
\(45h1 = 60h2\)
hence, \(45(2 - h2) = 60 h2\)
solve for h2 it should equal\(\frac{90}{105}\)
Solve for D by replacing value of h2 in the eqn \(60* h2\)
\(d =\frac{360}{7}\)
(C)
