The speed of a boatin still water is 9 km/hr and the speed of stream is 3 km/hr. The difference between the upstream speed and downstream speed will be:

Options

A. 6 km/hr
B. 5 km/hr
C. 3.5 km/hr
D. 7.5 km/hr

Answer

To solve the problem of finding the difference between the upstream speed and downstream speed of a boat, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given values**:
- Speed of the boat in still water = 9 km/hr
- Speed of the stream = 3 km/hr

2. **Calculate the upstream speed**:
- Upstream speed is calculated as the speed of the boat in still water minus the speed of the stream.
- Formula: Upstream Speed = Speed of Boat - Speed of Stream
- Calculation: Upstream Speed = 9 km/hr - 3 km/hr = 6 km/hr

3. **Calculate the downstream speed**:
- Downstream speed is calculated as the speed of the boat in still water plus the speed of the stream.
- Formula: Downstream Speed = Speed of Boat + Speed of Stream
- Calculation: Downstream Speed = 9 km/hr + 3 km/hr = 12 km/hr

4. **Find the difference between downstream speed and upstream speed**:
- The difference is calculated by subtracting the upstream speed from the downstream speed.
- Formula: Difference = Downstream Speed - Upstream Speed
- Calculation: Difference = 12 km/hr - 6 km/hr = 6 km/hr

### Final Answer:
The difference between the upstream speed and downstream speed is **6 km/hr**.

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