If a train 150 m long crosses a pole in 12 seconds, then what is the speed of the train in km per hr?

Options

A. 45
B. 60
C. 50
D. 75

Explanation

To find the speed of the train in kilometers per hour, we can follow these steps:

### Step 1: Identify the given values
- Length of the train = 150 meters
- Time taken to cross the pole = 12 seconds

### Step 2: Calculate the speed in meters per second
The formula for speed is:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]

Here, the distance is the length of the train (150 meters) and the time is 12 seconds. So we can plug in the values:
\[ \text{Speed} = \frac{150 \text{ meters}}{12 \text{ seconds}} \]

### Step 3: Perform the division
Calculating the above gives:
\[ \text{Speed} = 12.5 \text{ meters per second} \]

### Step 4: Convert the speed to kilometers per hour
To convert meters per second to kilometers per hour, we use the conversion factor:
\[ 1 \text{ m/s} = 3.6 \text{ km/h} \]

So, we multiply the speed in meters per second by 3.6:
\[ \text{Speed in km/h} = 12.5 \text{ m/s} \times 3.6 \]

### Step 5: Calculate the final speed
Calculating this gives:
\[ \text{Speed in km/h} = 45 \text{ km/h} \]

Thus, the speed of the train is **45 km/h**.