The speed of boat in still water is 8 km/hr. It covers a distance of km upstream in 8 hours. What is the speed (in km/hr)of the stream ?

Options

A. 1.5
B. 2
C. 3
D. 2.5

Answer

To solve the problem, we need to find the speed of the stream when a boat travels upstream. Here’s a step-by-step solution:

### Step 1: Understand the given information
- Speed of the boat in still water = 8 km/hr
- Distance covered upstream = 48 km
- Time taken to cover this distance = 8 hours

### Step 2: Calculate the speed of the boat upstream
When the boat travels upstream, the effective speed of the boat is reduced by the speed of the stream. Let's denote the speed of the stream as 's' km/hr.

The effective speed of the boat upstream can be expressed as:
\[ \text{Effective Speed} = \text{Speed of Boat} - \text{Speed of Stream} = 8 - s \text{ km/hr} \]

### Step 3: Use the formula for distance
We know that:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]

Substituting the values we have:
\[ 48 = (8 - s) \times 8 \]

### Step 4: Simplify the equation
Now, we simplify the equation:
\[ 48 = 64 - 8s \]

### Step 5: Rearrange the equation to solve for 's'
Rearranging the equation gives:
\[ 8s = 64 - 48 \]
\[ 8s = 16 \]

### Step 6: Solve for 's'
Now, divide both sides by 8:
\[ s = \frac{16}{8} = 2 \text{ km/hr} \]

### Conclusion
The speed of the stream is **2 km/hr**.

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