Question

Fran swims at a speed of 2.7 km/h in still water the lazy river flows at a speed of 0.3 km/h how long will it take Fran to swim 10km upstream? 10km downstream?

Answer 1

Let's start with defining velocity:

`Velocity = (distance)/(time)`
Therefore, we can arrange the eqation to look like:

`Time = (distance)/(velocity)`

a) How long will it take for Fran to swim 10km upstream?
* I assume that the lazy river flows at a speed of 0.3km/h upstream.
We now plug in the combined velocities and distance:

`Time = (10)/(2.7+0.3)`

`Time = (10)/(3) = 3.33`
∴ Fram can swim 10km upstream in 3.33 hours.

b) How long will it take for Fran to swim 10km downstream?
We do the same thing as a). You will notice that Fran's distance and velocity are negative since he is moving downstream. However, the velocity of the lazy river is still positive since it hasn't changed direction.

`Time = (-10)/(-2.7+0.3)`

`Time = (-10)/(-2.4) = 4.17`
∴Fran can swim 10km downstream in 4.17 hours.

I hope this helps! Let me know if you have any further questions.