Find the time taken by train 200 m long running at a speed of 60 km/hr to cross a signal post.

Options

A. 14 sec
B. 1 min
C. 30 sec
D. 12 sec

Answer

To find the time taken by a train that is 200 meters long running at a speed of 60 km/hr to cross a signal post, we can follow these steps:

### Step 1: Understand the Problem
The train will cross a signal post, which means the entire length of the train must pass the post. Therefore, the distance we need to consider is the length of the train, which is 200 meters.

### Step 2: Convert Speed from km/hr to m/s
The speed of the train is given as 60 km/hr. To use this in our calculations, we need to convert it to meters per second (m/s).

- **Conversion Formula**:
\[ \text{Speed (m/s)} = \text{Speed (km/hr)} \times \frac{1000 \text{ m}}{1 \text{ km}} \times \frac{1 \text{ hr}}{3600 \text{ s}} \]

- **Calculation**:
\[ 60 \text{ km/hr} = 60 \times \frac{1000}{3600} = 60 \times \frac{10}{36} = \frac{600}{36} = \frac{50}{3} \text{ m/s} \]

### Step 3: Use the Formula to Calculate Time
The formula to calculate time is:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]

- **Substituting the values**:
\[ \text{Time} = \frac{200 \text{ m}}{\frac{50}{3} \text{ m/s}} = 200 \times \frac{3}{50} = \frac{600}{50} = 12 \text{ seconds} \]

### Conclusion
The time taken by the train to cross the signal post is **12 seconds**.

---