Find the total distance covered by boat in each upstream and downstream in 7 hours if the speed of boat in still water and speed of current is 21 km/h and 3 km/h respectively?

Options

A. A)280 km
B. B)294 km
C. C)315 km
D. D)301 km

Answer

To solve the problem of finding the total distance covered by a boat in upstream and downstream in 7 hours, we can follow these steps:

### Step 1: Determine the speeds
- The speed of the boat in still water is given as 21 km/h.
- The speed of the current is given as 3 km/h.

### Step 2: Calculate the upstream speed
- The upstream speed (speed against the current) is calculated by subtracting the speed of the current from the speed of the boat in still water.

\[ \text{Upstream speed} = \text{Speed of boat} - \text{Speed of current} = 21 \text{ km/h} - 3 \text{ km/h} = 18 \text{ km/h} \]

### Step 3: Calculate the downstream speed
- The downstream speed (speed with the current) is calculated by adding the speed of the current to the speed of the boat in still water.

\[ \text{Downstream speed} = \text{Speed of boat} + \text{Speed of current} = 21 \text{ km/h} + 3 \text{ km/h} = 24 \text{ km/h} \]

### Step 4: Calculate the distance covered in upstream
- Distance is calculated using the formula: Distance = Speed × Time.
- For upstream, the time is 7 hours.

\[ \text{Distance upstream} = \text{Upstream speed} \times \text{Time} = 18 \text{ km/h} \times 7 \text{ hours} = 126 \text{ km} \]

### Step 5: Calculate the distance covered in downstream
- Similarly, for downstream:

\[ \text{Distance downstream} = \text{Downstream speed} \times \text{Time} = 24 \text{ km/h} \times 7 \text{ hours} = 168 \text{ km} \]

### Step 6: Calculate the total distance covered
- The total distance covered by the boat is the sum of the distances covered upstream and downstream.

\[ \text{Total distance} = \text{Distance upstream} + \text{Distance downstream} = 126 \text{ km} + 168 \text{ km} = 294 \text{ km} \]

### Final Answer
The total distance covered by the boat in upstream and downstream in 7 hours is **294 km**.

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