Places A and B are 100km apart on a highway. One car starts at A and another from B at the same time. If the cars travel in the same direction at different speeds, they meet in 5 hours. If they travel towards each other, they meet in 1 hour. What is the difference between the speeds of two cars?

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answer is B.

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Detailed Solution

Let the speed of the car at A be x kmph
and the speed of the car at B be y kmph
When car travels in same direction, Relative speed is x - y
Distance = 100 km
t = 5 hours
Therefore, Distance = S x T
100 = (x - y)5
x - y = 20……………….. (i)
When car travels in opposite direction, Relative speed is x + y
Distance = 100 km
t = 1 hour
Therefore, Distance = S x T
100 = (x + y)1
x + y = 100………..….. (ii)
Solving (i) and (ii)
x - y = 20

\frac{x + y = 100}{2 x = 120}

x = 60 km/h
y = 40 km/h
The difference of speed is 60 - 40 = 20 km/h
Hence, the correct option is 2.

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