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. MCQ with Answer and Explanation
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.
A. 8 km/h
B. 7.5 km/h
C. 8.5 km/h
D. 9 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Total distance = 24 + 24 + 24 = 72 km. Total time = 24/6 + 24/8 + 24/12 = 4 + 3 + 2 = 9 hours. Average speed = 72 / 9 = 8 km/h.
A thief is spotted by a policeman from a distance of 250 meters. When the policeman starts the chase, the thief also starts running. Assuming the speed of the thief to be 10 km/h and that of the policeman to be 12 km/h, how far will the thief have run before he is overtaken?
Explanation:
Relative speed = 12 - 10 = 2 km/h. Time taken to catch the thief = 0.25 km / 2 km/h = 1/8 hour. Distance run by the thief = Speed * Time = 10 km/h * (1/8) hour = 1.25 km = 1250 meters.
Explanation:
New speed = 3/5 of normal speed => New time = 5/3 of normal time. Difference = 2/3 of normal time = 16 minutes. Normal baseline time = (16 * 3) / 2 = 24 minutes.
Explanation:
Speed of runner-up = 100 / 12.5 = 8 m/s. When the winner crosses the finish line at 12 seconds, the distance covered by runner-up = 8 * 12 = 96 meters. Distance by which he lost = 100 - 96 = 5 meters.
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