A person has to cover a distance of 160 km. He covers the first half of the distance at 40 km/h. At what speed must he travel the remaining half to make the average speed for the whole journey 50 km/h? MCQ with Answer and Explanation
A person has to cover a distance of 160 km. He covers the first half of the distance at 40 km/h. At what speed must he travel the remaining half to make the average speed for the whole journey 50 km/h?
A. 66.67 km/h
B. 70 km/h
C. 60 km/h
D. 75 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let the required speed for the second half be x km/h. Using the average speed formula for equal halves: Average Speed = 2v1*v2 / (v1 + v2) => 50 = (2 * 40 * x) / (40 + x) => 50(40 + x) = 80x => 2000 + 50x = 80x => 30x = 2000 => x = 66.67 km/h.
A person travels a distance of 24 km at a speed of 6 km/h, another 24 km at 8 km/h and a third 24 km at 12 km/h. Find his average speed for the whole journey.
Two trains 100 meters and 120 meters long are running in the same direction at speeds of 72 km/h and 54 km/h respectively. In how much time will the faster train cross the slower train completely?
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