Time, Speed & Distance

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By walking at (dfrac{3}{4}^{th}) of his usual speed, a man reaches office 20 minutes later than usual. What is his usual time?


30 min


60 min


70 min


50 min

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Option(B) is correct

\(\dfrac{3}{4}\) of a man's usual speed means, he takes \(\dfrac{4}{3}\) of his usual time to cover the same distance, i.e. he takes


\(=\dfrac{1}{3}\) time extra.

\(\dfrac{1}{3}\) time is 20 minutes (given)

Usual time = $20\times 3$= 60 minutes

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