A train is $150\text{m}$ long running at a speed of $41\text{km/h}$. A man is running at $11\text{km/h}$ in the same direction as the train. In what time will the train pass the man?

When two objects move in the same direction, their relative speed is computed by subtracting the slower speed from the faster speed:
$$\text{Relative Speed}=41\text{km/h}-11\text{km/h}=30\text{km/h}$$

Convert the relative speed into meters per second ($\text{m/s}$):

$$\text{Relative Speed}=30\times \frac{5}{18}\text{m/s}=\frac{25}{3}\text{m/s}$$

The distance needed to cross the man is equal to the length of the train ($150\text{m}$):

$$\text{Time}=\frac{\text{Distance}}{\text{Relative Speed}}=\frac{150}{\frac{25}{3}}=\frac{150\times 3}{25}=6\times 3=18\text{ seconds}$$