A car covers four successive 3 km stretches at speeds of 10 km/h, 20 km/h, 30 km/h and 60 km/h respectively. Its average speed for this distance is: MCQ with Answer and Explanation
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.
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