Question

A river cruise boat sailed 80 miles down the Mississippi River for 4 hours. It took 5 hours to return. Find the rate of the cruise boat in still water and the rate of the current.

Answer 1

Rate of Cruise Boat is 18 miles per hour and Rate of Current is 2 miles per hour

Explanation:

Speed of boat is "x"

speed of current is "c"

We also know D = RT

Where D is distance, R is rate, T is time

For Downstream:

D = RT

80 = (x + c)(4)

For Upstream:

80 = (x - c)(5)

The first equation becomes: 20 = x + c

The second equation becomes: 16 = x -c

We add both the equation:

20 = x + c

16 = x - c

36 = 2x

x = 18

And, 20 = x + c, 20 = 18 + c, c = 2

Rate of Cruise Boat is 18 miles per hour and Rate of Current is 2 miles per hour