A train goes with a speed of 20 m/s what is the speed of train in km/h?

Options

A. 57 km/h
B. 72 km/h
C. 80 km/h
D. 120 km/h

Answer

To convert the speed of the train from meters per second (m/s) to kilometers per hour (km/h), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given speed**: The speed of the train is given as 20 m/s.

2. **Understand the conversion factors**:
- 1 kilometer (km) = 1000 meters (m)
- 1 hour (h) = 3600 seconds (s)

3. **Set up the conversion formula**:
To convert from m/s to km/h, we use the formula:
\[ \text{Speed in km/h} = \text{Speed in m/s} \times \frac{3600 \text{ s}}{1000 \text{ m}} \]

4. **Substitute the values**:
Substitute the speed of the train into the formula:
\[ \text{Speed in km/h} = 20 \text{ m/s} \times \frac{3600}{1000} \]

5. **Calculate the conversion**:
- First, simplify the fraction:
\[ \frac{3600}{1000} = 3.6 \]
- Now multiply:
\[ 20 \times 3.6 = 72 \]

6. **Final answer**:
The speed of the train in kilometers per hour is **72 km/h**.