Question
Ravi travels the first 40% of a certain distance at a
speed of 20 km/h, the next 30% at 10 km/h, and covers the remaining 30% at 12 km/h. Calculate Ravi's average speed for the entire journey in meters per second.Solution
Let the total distance be '100d' km. Time taken by Ravi to cover 40% distance = (40d/20) = '2d' hours Time taken by Ravi to cover 30% distance = (30d/10) = '3d' hours Time taken by Ravi to cover remaining distance: = (100d - 40d - 30d) ÷ 12 = (30d/12) = '2.5d' hours So, average speed = 100d ÷ (2d + 3d + 2.5d) = (100/7.5) = (40/3) km/h = (40/3) X (5/18) = (100/27) m/s
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