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# For the first hour Johnny drove at an average speed of x mph. For the

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Math Expert
Joined: 02 Sep 2009
Posts: 61549
For the first hour Johnny drove at an average speed of x mph. For the  [#permalink]

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27 Apr 2017, 01:48
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Difficulty:

45% (medium)

Question Stats:

72% (02:13) correct 28% (02:33) wrong based on 86 sessions

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For the first hour Johnny drove at an average speed of x mph. For the next 3 hours he averaged 20 mph less than the first hour. For the last 2 hours he drove at twice the rate of speed for the first hour. What was the average speed of the trip?

A. (8x - 60)/3
B. (4x - 30)/3
C. (3x - 20)/3
D. 2x - 30
E. (4x + 30)/3

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Re: For the first hour Johnny drove at an average speed of x mph. For the  [#permalink]

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27 Apr 2017, 02:28
Let the speed Johnny drove for the first hour be x.
Next 3 hours, he drove at x-20mph
In the last 2 hours, he drove at 2x
We know that distance = time * Speed
Distance traveled by him in 6 hours is x + 3(x-20) + 2x*2 = 8x - 60.
Average speed = 2(4x-30)/6 = (4x-30)/3(Option B)
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Re: For the first hour Johnny drove at an average speed of x mph. For the   [#permalink] 27 Apr 2017, 02:28
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