The speed of a train is 20% more than the speed of a car. Both start from point A at the same time and reach point B, 120 km away, at the same time. On the way, however, the train lost about 10 minutes while stopping at the stations. What is the speed of the car? MCQ with Answer and Explanation
The speed of a train is 20% more than the speed of a car. Both start from point A at the same time and reach point B, 120 km away, at the same time. On the way, however, the train lost about 10 minutes while stopping at the stations. What is the speed of the car?
A. 120 km/h
B. 100 km/h
C. 140 km/h
D. 80 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let car speed be c, then train speed is 1.2c. Time difference = 120/c - 120/(1.2c) = 10/60 hour. 120/c * (1 - 1/1.2) = 1/6 => 120/c * (0.2/1.2) = 1/6 => 120/c * (1/6) = 1/6 => c = 120 km/h.
Explanation:
Relative speed = 125 / 10 = 12.5 m/s = 12.5 * (18/5) = 45 km/h. Since they are in the same direction: Relative Speed = Speed of train - Speed of man => 45 = Speed of train - 5 => Speed of train = 50 km/h.
A person can row 10 km/h in still water. If it takes him exactly twice as long to row upstream as to row downstream over the same stretch, find the speed of the current.
Explanation:
Let speed of current be c km/h. Downstream speed = 10 + c, Upstream speed = 10 - c. Given: 2 * (10 - c) = 10 + c => 20 - 2c = 10 + c => 3c = 10 => c = 10/3 = 3.33 km/h.
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