The speed of two express locomotives are in the ratio 5 : 6. If the second locomotive maps 480 km in 4 hours, find the speed of the first locomotive. MCQ with Answer and Explanation
The speed of two express locomotives are in the ratio 5 : 6. If the second locomotive maps 480 km in 4 hours, find the speed of the first locomotive.
A. 110 km/h
B. 120 km/h
C. 90 km/h
D. 100 km/h
Answer: Option D
Solution (By JKSSB Mock Tests)
Speed of the second locomotive = 480 / 4 = 120 km/h. Ratio is 5:6, so 6 parts = 120 km/h => 1 part = 20 km/h. Speed of the first locomotive = 5 parts = 5 * 20 = 100 km/h.
The speeds of two running trains are in the ratio 7 : 9. Moving along parallel tracks in opposite directions, they take 4 seconds each to cross a telegraph post. Find the time taken by them to cross each other completely.
Explanation:
Let the speeds be 7x and 9x. Length of first train = 7x * 4 = 28x. Length of second train = 9x * 4 = 36x. Total distance to cross each other = 28x + 36x = 64x. Relative speed in opposite directions = 7x + 9x = 16x. Time taken = 64x / 16x = 4 seconds.
The speed of a boat in still water is 14 km/h and the speed of the current is 4 km/h. How much time will the boat take to cover a distance of 72 km downstream?
Explanation:
Downstream speed = Speed in still water + Speed of current = 14 + 4 = 18 km/h. Time taken = Distance / Downstream speed = 72 / 18 = 4 hours.
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