Question
A cyclist has to cover 180 km. She rides the first 20%
at 25 kmph, half of the distance at 30 kmph, and the remainder at 20 kmph. What is her approximate average speed?Solution
ATQ, Time for the first segment at 25 kmph = (180 × 0.20) / 25 = 1.44 hours Time for the second segment at 30 kmph = (180 × 1/2) / 30 = 3 hours Distance for the third segment = 180 - (180 × 0.20) - (180 × 1/2) = 180 - 36 - 90 = 54 km Time for the third segment at 20 kmph = 54 / 20 = 2.7 hours Average speed = 180 / (1.44 + 3 + 2.7) ≈ 32.73 kmph
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