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Radha reaches company 10 min late when she travels at a speed of 20kmph and she reaches 20 min early if she travels at a speed of 30kmph. At what speed she should travel to cover the office distance in 2 hours?1. 12 kmph2. 15 kmph3. 20 kmph4. 25 kmph5. 18 kmph |
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Answer» Correct Answer - Option 2 : 15 kmph GIVEN : Radha reaches company 10 min late when she travels at a speed of 20kmph She reaches 20 min early if she travels at a speed of 30kmph.
CONCEPT : Speed , Time & Distance
ASSUMPTION : Let the office distance for Radha be M km.
CALCULATION : Difference in time = 10 + 20 = 30 min = 30/60 hours Relative speed = M/20 - M/30 ⇒ M/20 - M/30 = 1/2 ⇒ 10M/600 = 1/2 ⇒ M = 30 The office distance for Radha is 30km. ∴ Required speed = distance/speed = 30/2 = 15kmph
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