A train covers a certain distance at a speed of 40 km/h and the next same distance with a speed of 70 km/h and the next same distance with a speed of 120 km/h. find the average speed?

Since the distance is same in all the conditions. Therefore, Average speed = 3xyz/(xy + yz + zx) Average speed = 3 x 40 x 70 x 120/(40 x 70 + 70 x 120 + 40 x 120) Average speed = 3 x 40 x 70 x 120/(2800 + 8400 + 4800) = 1008000/16000 = 63 km/hr

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^{th}time, then the speed of covering the remaining distance in the time left has to be: - Saket and Rakesh are brothers whose shops are located at a distance of 10km and 12km respectively from their home. Both of them start at the same time from home every day and reach their respective shops exactly at 8 am. When they decided to swap shops for a day, Saket started 4 minutes earlier than Rakesh. If both of them reached on time, what is the speed of Rakesh?
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