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A race car driver drives a miles in qualifying in p hours and then dri

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Bunuel
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A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   20 Mar 2017, 04:43
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A race car driver drives a miles in qualifying in p hours and then drives b miles in 2p hours. Which of the following represents the driver's average speed, in miles per hour, for the two sets of driving?

A. (a+b)/p
B. (a+b)/(3p)
C. 3p/(b-a)
D. 2(a+b)/(3p)
E. p/(2(a-b))
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B
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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   22 Mar 2017, 09:40
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Bunuel wrote:
A race car driver drives a miles in qualifying in p hours and then drives b miles in 2p hours. Which of the following represents the driver's average speed, in miles per hour, for the two sets of driving?

A. (a+b)/p
B. (a+b)/(3p)
C. 3p/(b-a)
D. 2(a+b)/(3p)
E. p/(2(a-b))



We can use the formula for average rate:

average rate = total distance/total time

average rate = (a + b)/(p + 2p) = (a + b)/(3p)

Answer: B
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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   20 Mar 2017, 06:20
Average Speed=Total Distance/Total Time
Total Distance=a+b
Total Time=p+2p=3p
Hence, the OA should be B
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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   20 Mar 2017, 10:45
Avg Speed = Total Distance Traveled / Total time of the Trip
Total Distance Traveled = a + b miles
Total Time = p + 2p = 3p

Avg Speed = (a+b)/3p

Ans:- B

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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   20 Mar 2017, 14:10
distance = speed x time
a = s x p

b = s x 2p

Combining these two together:

a + b = (s+s)/2 x (p+2p)
a + b = s x 3p
s = a+ b/3p which is answer B
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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   21 Mar 2017, 03:24
Bunuel wrote:
A race car driver drives a miles in qualifying in p hours and then drives b miles in 2p hours. Which of the following represents the driver's average speed, in miles per hour, for the two sets of driving?

A. (a+b)/p
B. (a+b)/(3p)
C. 3p/(b-a)
D. 2(a+b)/(3p)
E. p/(2(a-b))


total distance = a+b
total time = 3p

average speed = (a+b)/3p

Option B
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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink] New post   21 Mar 2017, 05:14
We can spot the solutions to eliminate: V=total distance /total time

The numerator in C, D & E does no represent distance. Eliminate them

We need total time. Eliminate A

Answer: B
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Re: A race car driver drives a miles in qualifying in p hours and then dri [#permalink]
21 Mar 2017, 05:14
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