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# Tara drove at an average speed of 50 miles per hour for the first 50

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Director
Joined: 04 Dec 2015
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Concentration: Technology, Strategy
Schools: ISB '19, IIMA , IIMB, XLRI
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Tara drove at an average speed of 50 miles per hour for the first 50 [#permalink]

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04 Sep 2017, 23:11
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Question Stats:

85% (00:53) correct 15% (01:28) wrong based on 66 sessions

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Tara drove at an average speed of 50 miles per hour for the first 50 miles of her trip and then at an average speed of 75 miles per hour for the remaining 50 miles of her trip. If she made no stops during the trip, what was Tara's average speed, in miles per hour, for the entire trip?

(A) 50
(B) 55
(C) 60
(D) 65
(E) 70
[Reveal] Spoiler: OA

Kudos [?]: 315 [0], given: 261

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Posts: 42248

Kudos [?]: 132527 [0], given: 12324

Re: Tara drove at an average speed of 50 miles per hour for the first 50 [#permalink]

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04 Sep 2017, 23:30
sashiim20 wrote:
Tara drove at an average speed of 50 miles per hour for the first 50 miles of her trip and then at an average speed of 75 miles per hour for the remaining 50 miles of her trip. If she made no stops during the trip, what was Tara's average speed, in miles per hour, for the entire trip?

(A) 50
(B) 55
(C) 60
(D) 65
(E) 70

(average speed) = (total distance)/(total time) = $$\frac{50 + 50}{\frac{50}{50} + \frac{50}{75}}=\frac{100}{\frac{5}{3}}=60$$.

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Math Expert
Joined: 02 Sep 2009
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Re: Tara drove at an average speed of 50 miles per hour for the first 50 [#permalink]

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04 Sep 2017, 23:38
1
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Expert's post
Bunuel wrote:
sashiim20 wrote:
Tara drove at an average speed of 50 miles per hour for the first 50 miles of her trip and then at an average speed of 75 miles per hour for the remaining 50 miles of her trip. If she made no stops during the trip, what was Tara's average speed, in miles per hour, for the entire trip?

(A) 50
(B) 55
(C) 60
(D) 65
(E) 70

(average speed) = (total distance)/(total time) = $$\frac{50 + 50}{\frac{50}{50} + \frac{50}{75}}=\frac{100}{\frac{5}{3}}=60$$.

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Re: Tara drove at an average speed of 50 miles per hour for the first 50 [#permalink]

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06 Sep 2017, 03:37
sashiim20 wrote:
Tara drove at an average speed of 50 miles per hour for the first 50 miles of her trip and then at an average speed of 75 miles per hour for the remaining 50 miles of her trip. If she made no stops during the trip, what was Tara's average speed, in miles per hour, for the entire trip?

(A) 50
(B) 55
(C) 60
(D) 65
(E) 70

Either use the total distance/ total time concept

or the Average speed eqn =2V1V2/V1+V2.

So 2*50*75/(50+75)= 60
Ans:C

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Re: Tara drove at an average speed of 50 miles per hour for the first 50 [#permalink]

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11 Sep 2017, 11:05
sashiim20 wrote:
Tara drove at an average speed of 50 miles per hour for the first 50 miles of her trip and then at an average speed of 75 miles per hour for the remaining 50 miles of her trip. If she made no stops during the trip, what was Tara's average speed, in miles per hour, for the entire trip?

(A) 50
(B) 55
(C) 60
(D) 65
(E) 70

We can use the following formula:

average speed = (distance 1 + distance 2)/(time 1 + time 2)

We see that time 1 = 1 hour, time 2 = 50/75 = 2/3 hours, and distance 1 = distance 2 = 50 miles. Thus:

average = (50 + 50 )/(1 + 2/3)

average = 100/(5/3) = 300/5 = 60 mph.

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Re: Tara drove at an average speed of 50 miles per hour for the first 50   [#permalink] 11 Sep 2017, 11:05
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