Question

PLEASE HELP FAST!!!!

A man goes fishing in a river and wants to know how long it will take him to get 10km upstream
to his favourite fishing location. The speed of the current is 3 km/hr and it takes his boat twice
as long to go 3km upstream as is does to go 4km downstream. How long will it take his boat to
get to his fishing spot?

Answer 1

Time = 25/9 hr

Explanation:

Let speed of boat in still water is x km/hr

then, speed in downstream equals to "x + 3"km/hr

and speed in upstream equals to "x - 3" km/hr

We also know that time taken to travel 3km in upstream is twice as time taken to travel 4km in downstream.

so, using time = distance/speed

3/x- 3 = 2 × (4/x + 3)

3x + 9 = 8x -24

5x = 33

x = 33/5 km/hr

Net speed in upstream = 33/5 - 3 = 18/5 km/hr

So, Time taken to travel 10km upstream = distance /speed

= (10 × 5) / 18 = 25/9 hr

Time = 25/9 hr