A boat can travel with a speed of 13 km/hr in still water . If the speed of stream is 4 km /hr in the same direction , time taken by boat to go 63 km in opposite direction is

Options

A. 9 hrs
B. 4 hrs
C. 7 hrs
D. `3(9)/(17)` hrs

Answer

To solve the problem step by step, we need to determine the effective speed of the boat when it is traveling against the current of the stream and then calculate the time taken to cover the distance of 63 km.

### Step 1: Identify the speeds
- Speed of the boat in still water = 13 km/hr
- Speed of the stream = 4 km/hr

### Step 2: Calculate the effective speed of the boat in the opposite direction
When the boat is traveling against the stream, the effective speed of the boat is given by:
\[ \text{Effective speed} = \text{Speed of the boat} - \text{Speed of the stream} \]
\[ \text{Effective speed} = 13 \text{ km/hr} - 4 \text{ km/hr} = 9 \text{ km/hr} \]

### Step 3: Use the formula for time
The formula to calculate time is:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]
Here, the distance to be covered is 63 km and the effective speed is 9 km/hr.

### Step 4: Calculate the time taken
Substituting the values into the formula:
\[ \text{Time} = \frac{63 \text{ km}}{9 \text{ km/hr}} = 7 \text{ hours} \]

### Final Answer
The time taken by the boat to go 63 km in the opposite direction is **7 hours**.

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