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Jenny drove to the gym with an average speed of 60 miles per hour. On
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01 Oct 2018, 08:20
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A
B
C
D
E
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Question Stats:
74% (01:52) correct 26% (01:22) wrong based on 136 sessions
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Jenny drove to the gym with an average speed of 60 miles per hour. On her way back she drove the same route with an average speed of 80 miles per hour. What was er average speed for the whole trip in mph?
Re: Jenny drove to the gym with an average speed of 60 miles per hour. On
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01 Oct 2018, 08:35
bettatantalo wrote:
Jenny drove to the gym with an average speed of 60 miles per hour. On her way back she drove the same route with an average speed of 80 miles per hour. What was er average speed for the whole trip in mph?
a) 60
b) 68
c) 68 4/7
d) 70
e) 74 3/8
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Direct formula... \(\frac{2*a*b}{a+b}=\frac{2*60*80}{60+80}\)=960/14=480/7=68 4/7
C
Otherwise.. Let the distance be d.. d/60 +d/80 =3d+4d/240.. = total time taken Average speed = 2d/(7d/240)=480/7
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01 Oct 2018, 10:23
Top Contributor
bettatantalo wrote:
Jenny drove to the gym with an average speed of 60 miles per hour. On her way back she drove the same route with an average speed of 80 miles per hour. What was er average speed for the whole trip in mph?
a) 60
b) 68
c) 68 4/7
d) 70
e) 74 3/8
Another approach is to assign a "nice" value (one that works well with 60 mph and 80 mph) to the distance to the gym. So, let's say the distance is 480 miles (a long commute indeed!)
Average speed = (total distance traveled)/(total travel time)
TOTAL distance = 480 miles + 480 miles = 960 miles
Now let's calculate the TOTAL travel time.
time = distance/speed So, travel time TO the gym = 480/60 = 8 hours And travel time FROM the gym = 480/80 = 6 hours So, TOTAL travel time = 8 hours + 6 hours = 14 hours
So, average speed = 960 miles/14 hours = 480/7 miles per hour = 68 4/7 miles per hour
Re: Jenny drove to the gym with an average speed of 60 miles per hour. On
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02 Oct 2018, 01:41
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bettatantalo wrote:
Jenny drove to the gym with an average speed of 60 miles per hour. On her way back she drove the same route with an average speed of 80 miles per hour. What was er average speed for the whole trip in mph?
a) 60
b) 68
c) 68 4/7
d) 70
e) 74 3/8
source gmat tutor
If the distance from home to gym is D, then total distance =2D time from Home to Gym T1=D/60 time from Gym to home T2=D/80
average speed = total distance/(T1+T2) = 2D/(D/60+D80) =68 4/7 answer is C
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Re: Jenny drove to the gym with an average speed of 60 miles per hour. On
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03 Oct 2018, 17:42
bettatantalo wrote:
Jenny drove to the gym with an average speed of 60 miles per hour. On her way back she drove the same route with an average speed of 80 miles per hour. What was er average speed for the whole trip in mph?
a) 60
b) 68
c) 68 4/7
d) 70
e) 74 3/8
We can let the distance each way = 240 miles and use the formula: average rate = total distance/total time:
Re: Jenny drove to the gym with an average speed of 60 miles per hour. On
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26 Sep 2019, 06:34
Average speed from her home to the gym = 60mph Therefore time taken from her home to the gym = 240/60 = 4 hours Average speed from the gym to her home = 80mph Therefore time taken from the gym to her home = 240/80 = 3 hours Total distance = 480 total time taken = 7 hours Average speed = Total Distance/Total Time = 480/7= 68 4/7 Therefore C is the correct answer
gmatclubot
Re: Jenny drove to the gym with an average speed of 60 miles per hour. On
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26 Sep 2019, 06:34