A boat covers 800 meters in 600 seconds against the stream and returns downstream in 5 minutes. What is the speed of the boat in still water?

2 m/sec

Given:

• Distance = 800 m
• Upstream time = 600 s
• Downstream time = $5 \text{ min} = 300 \text{ s}$

Step 1: Calculate upstream and downstream speeds

$v = \frac{d}{t}$

Upstream speed:

$\frac{800}{600} = \frac{4}{3} \text{ m/s}$

Downstream speed:

$\frac{800}{300} = \frac{8}{3} \text{ m/s}$

Step 2: Find the speed in still water

$\text{Speed in still water} = \frac{\text{Upstream speed} + \text{Downstream speed}}{2}$

$= \frac{\frac{4}{3} + \frac{8}{3}}{2} = \frac{12/3}{2} = \frac{4}{2} = 2 \text{ m/s}$