Excluding stoppages, the speed of a bus is 60 km/h and including stoppages, it is 51 km/h. For how many minutes does the bus stop per hour?

Options

A. 9
B. 12
C. 8
D. 10

Answer

To solve the problem, we need to determine how many minutes the bus stops per hour based on its speeds excluding and including stoppages.

### Step-by-Step Solution:

1. **Identify the Speeds**:
- Speed excluding stoppages = 60 km/h
- Speed including stoppages = 51 km/h

2. **Calculate the Distance Covered in One Hour**:
- At a speed of 60 km/h, the distance covered in one hour (without stoppages) is 60 km.
- At a speed of 51 km/h, the distance covered in one hour (including stoppages) is 51 km.

3. **Determine the Difference in Distance**:
- The difference in distance due to stoppages = Distance without stoppages - Distance with stoppages
- Difference = 60 km - 51 km = 9 km

4. **Calculate the Time Lost Due to Stoppages**:
- The bus covers 9 km less in the hour due to stoppages.
- To find out how long the bus stops, we need to determine how long it would take to cover the 9 km at the speed of 60 km/h.
- Time = Distance / Speed = 9 km / 60 km/h = 0.15 hours

5. **Convert Time from Hours to Minutes**:
- Since 1 hour = 60 minutes, we convert 0.15 hours to minutes.
- Time in minutes = 0.15 hours × 60 minutes/hour = 9 minutes

### Conclusion:
The bus stops for **9 minutes** per hour.