Question

Read the word problem below.

Chan rows at a rate of eight miles per hour in still water. On Wednesday, it takes him three hours to row upstream from his house to the park. He rows back home, and it takes him two hours. What is the speed of the current?

Answer 1

1.6 mph

Explanation:

Distance, speed, and time are related by ...

distance = speed × time

We assume that the distances up and back are the same, so for a current speed of c, we have ...

3(8 -c) = 2(8 +c)

24 -3c = 16 +2c . . . eliminate parentheses

8 = 5c . . . . . . . . . . add 3c-16 to both sides

c = 8/5 = 1.6 . . . . . divide by 5

The speed of the current is 1.6 miles per hour.

Answer 2

1 3/5 miles/hr

Explanation:

Let C be the speed of the current

Let D be the distance between Chan's house and the park

We know that Distance, D, is = Speed x Time

-----

Chan's speed going upstream is (8 - C)mph.

That gives us:

D = (8-C)(3 hr)

Chan's speed going downstream is (8+C)mph

So we have:

D = (8+C)(2 hr)

We know that the d is the same for these two equations, so:

(8-C)(3 hr) = (8+C)(2 hr)

24 - 3C = 16 + 2C

5C = 8

C = (8/5) or 1 3/5 mph