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# Car M was driving on a highway at a constant speed of 50 miles per hou

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Joined: 25 Dec 2018
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Car M was driving on a highway at a constant speed of 50 miles per hou  [#permalink]

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10 Mar 2019, 09:57
1
4
00:00

Difficulty:

45% (medium)

Question Stats:

67% (02:36) correct 33% (02:39) wrong based on 46 sessions

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Car M was driving on a highway at a constant speed of 50 miles per hour. If Car N was 3 miles behind Car M 20 minutes ago and 2 miles ahead of Car M 5 minutes ago, what was the speed of Car N? Assume that Car N was driving at a constant speed.

A. 60 miles per hour

B. 70 miles per hour

C. 90 miles per hour

D. 100 miles per hour

E. 110 miles per hour
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Joined: 02 Aug 2009
Posts: 8006
Re: Car M was driving on a highway at a constant speed of 50 miles per hou  [#permalink]

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10 Mar 2019, 20:00
3
mangamma wrote:
Car M was driving on a highway at a constant speed of 50 miles per hour. If Car N was 3 miles behind Car M 20 minutes ago and 2 miles ahead of Car M 5 minutes ago, what was the speed of Car N? Assume that Car N was driving at a constant speed.

A. 60 miles per hour

B. 70 miles per hour

C. 90 miles per hour

D. 100 miles per hour

E. 110 miles per hour

Car M travels at 50mph, and car N covers (3+2)miles in (20-5) minutes over car M. So it travels 5 miles more in 15 minutes or 5*4 in 15*4 min, that is 20 miles in an hour.
Thus the speed of car N is 50+20 or 70 mph.

B
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Re: Car M was driving on a highway at a constant speed of 50 miles per hou  [#permalink]

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31 Mar 2019, 00:32
1
As the cars travel in the same direction the relative speed is X-50.
D/S=T, (2-(-3))/(X-50) = 15/60. Solving it 5/(X-50)=1/4, 20=X-50, X=70
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Re: Car M was driving on a highway at a constant speed of 50 miles per hou   [#permalink] 31 Mar 2019, 00:32
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