The speed of a bus is 72 kmph. The distance covered by the bus in 5 sec is [Indian Railway Gr. 'D' Exam, 2014]

### Concept & Formula To find distance in meters given time in seconds, the speed must first be converted from kilometers per hour (kmph) to meters per second (m/s). $$ \text{Speed in m/s} = \text{Speed in kmph} \times \frac{5}{18} $$ $$ \text{Distance} = \text{Speed} \times \text{Time} $$ ### Step-by-Step Solution 1. **Convert Speed:** Convert 72 kmph to m/s. $$ 72 \times \frac{5}{18} = 4 \times 5 = 20 \text{ m/s} $$ 2. **Calculate Distance:** Use the converted speed and the given time (5 seconds). $$ \text{Distance} = 20 \text{ m/s} \times 5 \text{ sec} = 100 \text{ meters} $$ ### Exam Strategy & Shortcut Memorize common conversions: $18 \text{ kmph} = 5 \text{ m/s}$. Since $72 \text{ kmph} = 4 \times 18 \text{ kmph}$, the speed is $4 \times 5 \text{ m/s} = 20 \text{ m/s}$. The distance is $20 \times 5 = 100 \text{ m}$. ### Common Pitfall A major mistake is forgetting to convert units and simply multiplying $72 \times 5$, leading to incorrect units and answers. Always ensure unit consistency. ### Final Answer Therefore, the correct answer is **100 m**.