A bus traveled from its depot to its destination at an average speed of 60 kilometers per hour. On its return to the depot along the same route, the bus traveled at an average speed of only 40 kilometers per hour, making the trip 4 hours longer. What is the total distance of the round trip?

A. 360 kilometers
B. 400 kilometers
C. 600 kilometers
D. 800 kilometers
E. 960 kilometers

Kudos for a correct solution.
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The difference of speed (60-40 = 20 Kmph) is causing the delay of 4 hours

Distance = Speed x Time

Case 1: Distance = 60 x T While driving from Depot to Destination
Case 2: Distance = 40 x (T+4) While returning from Destination to Depot

Since the Distance Travelled is same in both cases therefore

60 x T = 40 x (T+4)
i.e. 20 T = 160
i.e. T = 8 Hours

i.e. (One side) Distance = 60 x T = 60 x 8 = 480
Total Distance of the round trip = 480 x 2 = 960 Km

Answer: Option E
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Think about the concepts. The distance for the 2 trips is the same. So if RT = D, then R1T1 = R2T2.

You can now plug in the infromation:

60T = 40 (T + 4).

Solving T = 8


If the time for the first half took 8 hours and the speed was 60km/hour 8 x 60 = 480.


The total distance is then 480 + 480.
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One way to think about this is that the Distance of the two trips is same. Thus, 40t + 4 hours = 60t. Further, since t will be the same on each side of the equation, you can subtract 40t from each side. That leaves you with 4 hours at 40kph, or 160 km = 20t, or t=8 hours. Finally, since the question asks for the distance of the roundtrip, you can find this by 60 x 8 x 2, or 960 km.
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Speed*time=distance
Let time for trip one be x
Trip1- d1= 60*x
Trip2- d2= 40*(x+4)
D1=D2
So x= 8
So d1= 480
d2= 480
Total distance =960 kms
E

Let one way distance=d
Now, d/60+4=d/40
d/40-d/60=4
3d-2d/120=4
d=480
2d=960 km
Answer E

800score Official Solution:

The distance formula is Distance = Rate × Time. To solve this question, set x as the length of time (in hours) for the first trip. The distance to the destination city is 60 × x, where rate = 60 and time = x. The return trip was 4 hours longer, so its distance is 40(x + 4).

Since we know the distances are the same, we can set them equal to each other and solve for x:
60x = 40(x + 4)
60x = 40x + 160
20x = 160
x = 8.

So, the trip took 8 hours, and its distance is 8 × 60 = 480 kilometers. The question asks for the roundtrip distance, so we double the length of the one-way trip: 480 × 2 = 960 kilometers.

The correct answer is choice (E).
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