A cross-country runner covers the sides of an equilateral triangular course at speeds of 8 km/h, 12 km/h and 24 km/h respectively. Find his average speed for the whole round. MCQ with Answer and Explanation
A cross-country runner covers the sides of an equilateral triangular course at speeds of 8 km/h, 12 km/h and 24 km/h respectively. Find his average speed for the whole round.
A. 12 km/h
B. 16 km/h
C. 10 km/h
D. 14 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let each side of the triangular course be 24 km. Total perimeter = 3 * 24 = 72 km. Total time taken = 24/8 + 24/12 + 24/24 = 3 + 2 + 1 = 6 hours. Average speed = 72 / 6 = 12 km/h.
The speed indices of two sprinters are in the ratio 3 : 4. If the first sprinter requires 24 seconds to wrap up a bend, how much time does the second sprinter require?
Explanation:
Ratio of speeds = 3:4, so ratio of times required = 4:3. Given 4 parts = 24 seconds => 1 part = 6 seconds. Time for the second sprinter = 3 parts = 3 * 6 = 18 seconds.
A high-speed train clears a structural platform watchpost signal pillar in 6 seconds and passes across the full platform itself, which measures 200 meters long, in 16 seconds. Find the speed index of the train in km/h.
Explanation:
Time taken to cross the platform span alone = 16 - 6 = 10 seconds. Speed of train = 200 / 10 = 20 m/s. In km/h index = 20 * (18/5) = 72 km/h.
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