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11 Dec 2016, 08:23
Kudos
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D
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Difficulty:
35%
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Question Stats:
75% (02:42) correct
25%
(02:46)
wrong
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If a freight train travels at an average speed of 30 mph, it will arrive at its destination 1.5 hours late. If the train instead travels at an average speed of 45 mph, it will arrive 1 hour early. At what average speed, in miles per hour, should the train travel in order to arrive at its destination exactly on time?
A) 33
B) 35
C) 36
D) 37.5
E) 39
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A) 33
B) 35
C) 36
D) 37.5
E) 39
If u liked my post, please press kudos!
13 Dec 2016, 17:47
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souvonik2k
We are given that if a freight train travels at an average speed of 30 mph, it will arrive at its destination 1.5 hours late. We can let T = the time it would take the train to arrive on time, and since distance = rate x time, the distance traveled by the train can be expressed as:
Distance = 30(T + 1.5) = 30T + 45
We are also given that if the train instead travels at an average speed of 45 mph, it will arrive 1 hour early. Thus, the distance traveled by the train can be also expressed as:
Distance = 45(T - 1) = 45T - 45
Since the distance traveled by the train, whether it travels at 30 mph or at 40 mph, is the same, we can now set our two distance values to each other and determine T:
30T + 45 = 45T - 45
15T = 90
T = 6
We can now determine the distance:
Distance = 30(6) + 45 = 180 + 45 = 225
Thus, the rate needed to arrive on time is 225/6 = 37.5 mph.
Answer: D
General Discussion
11 Dec 2016, 10:34
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The distance is the same whether you arrive early or late.
30(t+1.5)=45(t-1)
2t+3=3t-3
t=6
So distance is 45(5)=225
And t=6
Avg speed =225/6=37.5
D.
Sent from my SAMSUNG-SM-G935A using GMAT Club Forum mobile app
30(t+1.5)=45(t-1)
2t+3=3t-3
t=6
So distance is 45(5)=225
And t=6
Avg speed =225/6=37.5
D.
Sent from my SAMSUNG-SM-G935A using GMAT Club Forum mobile app
