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The distance between cities A and B is 120 miles. A car travels from A

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The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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21 Jun 2017, 02:06
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94% (01:01) correct 6% (00:50) wrong based on 122 sessions

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The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour and returns from B to A along the same route at 40 miles per hour. What is the average speed for the round trip?

(A) 48
(B) 50
(C) 52
(D) 56
(E) 58

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Re: The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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21 Jun 2017, 02:17
Bunuel wrote:
The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour and returns from B to A along the same route at 40 miles per hour. What is the average speed for the round trip?

(A) 48
(B) 50
(C) 52
(D) 56
(E) 58

Total Distance $$= 120 + 120 = 240$$ miles

Time taken to travel from A to B = Distance / speed $$= \frac{120}{60} = 2$$ hours

Time taken to travel from B to A = Distance / speed $$= \frac{120}{40} = 3$$ hours

Total Time Taken $$= 2 + 3 = 5$$ hours

Average Speed = Total Distance Traveled / Total Time Taken

Average Speed $$= \frac{240}{5} = 48$$ miles / hr . Answer (A)...
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Re: The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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21 Jun 2017, 02:26
From A to B Car took 2 hrs
From B to A Car took 3 hrs

D = 240, t = 5 S = 240/5 = 48 km/h

Second approach could be

(60*2 + 40*3)/(2+3) = 48
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The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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21 Jun 2017, 02:33
Given:
a(speed of travel from A to B) : 60 miles/hour
b(speed of travel from B to A) : 40 miles/hour

Average speed = $$\frac{(2*a*b)}{(a+b)}$$

Substituting values,
Average speed = $$\frac{(2*40*60)}{(40+60)}$$
= $$\frac{(2*40*60)}{(100)} = 2*4*6 = 48$$(Option A)

P.S this is the formula for average speed, when the distance traveled across both
the legs is the same.
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Re: The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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21 Jun 2017, 06:27
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Bunuel wrote:
The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour and returns from B to A along the same route at 40 miles per hour. What is the average speed for the round trip?

(A) 48
(B) 50
(C) 52
(D) 56
(E) 58

Average speed = (TOTAL distance)/(TOTAL travel time)

TOTAL distance = 120 + 120 = 240 miles

A car travels from A to B at 60 miles per hour....
time = distance/speed
So, time = 120/60 = 2 hours

...and returns from B to A along the same route at 40 miles per hour
time = distance/speed
So, time = 120/40 = 3 hours

TOTAL travel time = 2 hours + 3 hours = 5 hours

Average speed = (240)/(5)
= 48 miles per hour

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Re: The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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21 Jun 2017, 06:37
Bunuel wrote:
The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour and returns from B to A along the same route at 40 miles per hour. What is the average speed for the round trip?

(A) 48
(B) 50
(C) 52
(D) 56
(E) 58

Breakdown and solve -
Quote:
The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour

Time required for onward journey = 2 hour
Quote:
returns from B to A along the same route at 40 miles per hour.

Time required for onward journey = 3 hour

Total distance is 240 miles
Total Time is 5 Hours

So, Average speed is 48 miles/hr , answer will be (A)
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Re: The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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22 Jun 2017, 01:27
Bunuel wrote:
The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour and returns from B to A along the same route at 40 miles per hour. What is the average speed for the round trip?

(A) 48
(B) 50
(C) 52
(D) 56
(E) 58

Distance between A and B = 120 miles.
1st : Car travels from A to B at 60 miles/hour. Time of travel = 120/60 = 2 hour.
2nd : Car travels from B to A at 40 miles/hour. Time of travel = 120/40 = 3 hour

Average speed of round trip = (120+120)/(2+3) = 48 miles per hour.

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Re: The distance between cities A and B is 120 miles. A car travels from A  [#permalink]

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13 Aug 2017, 13:17
Bunuel wrote:
The distance between cities A and B is 120 miles. A car travels from A to B at 60 miles per hour and returns from B to A along the same route at 40 miles per hour. What is the average speed for the round trip?

(A) 48
(B) 50
(C) 52
(D) 56
(E) 58

Easy. This is obviously a round trip question so we just apply some basic formulas

Total Distance= AvgSpeed * Total Time

120/60 =2
120/40 =3

240 = Avgspeed * 5
Avgspeed= 240/5

48

A
Re: The distance between cities A and B is 120 miles. A car travels from A   [#permalink] 13 Aug 2017, 13:17
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