Question

A train of length 140m moves at 72kmph. What is the time taken to cross a man jogging at 9kmph in the same direction?

Answer 1

Answer:

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Explanation:

$The \: length \: of \: train \: isin \: metre. \\ So, \: \: \: Speed \: = 72 \times \frac{5}{18} m /s = 20 \: m/s \\ and \: \\ Speed \: of \: man \: = 9 \times \frac{5}{18} = \frac{5}{2} m/s \\ \: Relative \: speed \: = speed \: of \: train \: - speed \: of \: man \: = 20 - \frac{5}{2} m/s = \frac{35}{2} m/s \\ therefore, \: \\ time \: taken \: to \: cross \:the \: man \: = \frac{length \: of \: train}{relative \: speed} = \frac{140}{ \frac{35}{2} } = \frac{140 \times 2}{35} = 8 \: sec \\ \\ \\ \\ Hence, \: the \: train \: take \: 8sec \: to \: cross \: the \: moving \: man$