Question

Fran swims at a speed of 2.8 mph in still water. The Lazy River flows at a speed of 0.6 mph. How long will it take Fran to swim 2.2 mi? upstream? 2.2 mi? downstream?

Answer 1

Answer:

1. Upstream Time:  1 hour (or 60 minutes)

2. Downstream Time: 0.65 hour (or 39 minutes)

Step-by-step explanation:

The time it will take goes by the distance formula:

$D=RT$, where D is the distance, R is the rate (speed), and T is the time.

For Upstream, you are going against the current, so your still water speed slows down. So upstream rate is still water rate - stream rate. So 2.8 - 0.6 = 2.2mph

Time it will take him to swim 2.2 miles, is:

$D=RT\\2.2=2.2(T)\\T=\frac{2.2}{2.2}=1$

So, 1 hour

For Downstream, you are going with the current, so your still water speed increases. So downstream rate is still water rate + stream rate. So 2.8 + 0.6 = 3.4 mph

Time it will take him to swim 2.2 miles, is:

$D=RT\\2.2=3.4(T)\\T=\frac{2.2}{3.4}=0.65$

So, 0.65 hours (or 0.65*60=39 minutes)