The speed of two trains are in the ratio 4 : 5. If the second train covers 300 km in 3 hours, find the speed of the first train. MCQ with Answer and Explanation
The speed of two trains are in the ratio 4 : 5. If the second train covers 300 km in 3 hours, find the speed of the first train.
A. 85 km/h
B. 80 km/h
C. 90 km/h
D. 75 km/h
Answer: Option B
Solution (By JKSSB Mock Tests)
Speed of the second train = 300 / 3 = 100 km/h. Speed ratio is 4:5, so 5 parts = 100 km/h => 1 part = 20 km/h. Speed of the first train = 4 parts = 4 * 20 = 80 km/h.
Explanation:
Let total distance be 100 km. First section = 30 km; Time = 30 / 30 = 1 hour. Second section = 70 km; Time = 70 / 42 = 5/3 hours. Total time = 1 + 5/3 = 8/3 hours. Average speed = 100 / (8/3) = 300 / 8 = 37.5 km/h.
In a 1000m dash, competitor M beats B by 80 meters, and B beats C by 50 meters. Assuming uniform velocities, by how many meters does M beat C in that same race?
Explanation:
When M runs 1000m, B runs 920m. When B runs 1000m, C runs 950m. When B runs 920m, C runs 950 * (920/1000) = 95 * 9.2 = 874m. Therefore, M beats C by 1000 - 874 = 126 meters.
The speeds of two bodies are in the ratio 5 : 6. If they clear the same sector distance, and the slower car takes 3 hours, how much time does the faster car take?
Explanation:
Ratio of speeds = 5:6, so ratio of times taken = 6:5. Slower car takes 6 parts = 3 hours => 1 part = 0.5 hours. Time for faster car = 5 parts = 5 * 0.5 = 2.5 hours.
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