Find the time taken by a train 180 m long , running at 72 km per hour , in crossing an electric pole .

Answer

To solve the problem of finding the time taken by a train 180 m long, running at 72 km/h, to cross an electric pole, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given values:**
- Length of the train (distance to be covered) = 180 m
- Speed of the train = 72 km/h

2. **Convert the speed from km/h to m/s:**
- We know that:
\[ 1 \text{ km} = 1000 \text{ m} \quad \text{and} \quad 1 \text{ hour} = 3600 \text{ seconds} \]
- To convert km/h to m/s, we use the formula:
\[ \text{Speed in m/s} = \text{Speed in km/h} \times \frac{1000 \text{ m}}{3600 \text{ s}} \]
- Plugging in the values:
\[ \text{Speed in m/s} = 72 \times \frac{1000}{3600} \]
- Simplifying this:
\[ = 72 \times \frac{10}{36} = 72 \times \frac{5}{18} = 20 \text{ m/s} \]

3. **Calculate the time taken to cross the electric pole:**
- The time taken to cross an object (in this case, an electric pole) can be calculated using the formula:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]
- Here, the distance is the length of the train (180 m) and the speed is 20 m/s:
\[ \text{Time} = \frac{180 \text{ m}}{20 \text{ m/s}} = 9 \text{ seconds} \]

### Final Answer:
The time taken by the train to cross the electric pole is **9 seconds**.

---