The speed of a boat in still water is 10 km/hr. If its speed downstream be 13 km/hr, then speed of the stream is -----

Options

A. 1.5 km/hr
B. 3 km/hr
C. 11.5 km/hr
D. 5.75 km/hr

Answer

To solve the problem, we need to find the speed of the stream when we know the speed of the boat in still water and the speed of the boat downstream.

**Step-by-step solution:**

1. **Identify the given values:**
- Speed of the boat in still water (X) = 10 km/hr
- Speed of the boat downstream (U) = 13 km/hr

2. **Understand the relationship between the speeds:**
- The speed of the boat downstream is the sum of the speed of the boat in still water and the speed of the stream (Y).
- This can be expressed as:
\[ U = X + Y \]

3. **Substitute the known values into the equation:**
- We know U = 13 km/hr and X = 10 km/hr. Substitute these values into the equation:
\[ 13 = 10 + Y \]

4. **Solve for the speed of the stream (Y):**
- Rearranging the equation to isolate Y gives:
\[ Y = 13 - 10 \]
- Therefore:
\[ Y = 3 \text{ km/hr} \]

5. **Conclusion:**
- The speed of the stream is 3 km/hr.

**Final Answer:**
The speed of the stream is **3 km/hr**.

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