Question

A train 150 metres long passes a pole in 15 seconds; what is the speed of the train in km/hr?

• A. 30 km/hr
• B. 36 km/hr
• C. 40 km/hr
• D. 45 km/hr

Hint:

Important formulas for train problems: \[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \] If a train passes a pole: \[ \text{Distance} = \text{Length of train} \] Conversion rule: \[ 1 \text{ m/s} = 3.6 \text{ km/hr} \] Memory trick: \[ \textbf{Pole → Only Train Length} \]

Answer 1

The Correct Option is B

Concept:
When a train passes a pole or a standing object, the distance covered by the train is equal to the length of the train. The speed of the train can be calculated using the basic formula: \[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \] Here:

• Distance = Length of the train
• Time = Time taken to completely pass the pole

After calculating speed in metres per second (m/s), we convert it into kilometres per hour (km/hr) using: \[ 1 \text{ m/s} = 3.6 \text{ km/hr} \]
Step 1: Identify the given values.
\[ \text{Length of train} = 150 \text{ metres} \] \[ \text{Time taken} = 15 \text{ seconds} \]
Step 2: Calculate speed in m/s.
\[ \text{Speed} = \frac{150}{15} \] \[ = 10 \text{ m/s} \]
Step 3: Convert m/s to km/hr.
\[ 10 \times 3.6 = 36 \text{ km/hr} \]
Step 4: Final result.
\[ \boxed{36 \text{ km/hr}} \]