# The speed of a stream is 5 mph. A boat travels 10 miles upstream in the same time it takes to travel 20 miles downstream. What is the speed of the boat in still water?

##### 1 Answer

Nov 19, 2017

OK, the first problem is to translate the question into algebra. Then we’ll see if we can solve the equations.

#### Explanation:

We’re told that v(boat) + v(stream) = 20, i.e. going downstream;

that v(boat) - v(stream) = 10 (going upstream)

and that v(stream) = 5.

So from the 2nd equation: v(boat) = 10 + v(stream) = 10 + 5

So v(boat) = 15.

Check by putting this value back into the first equation

15 + v(stream) = 15 + 5 = 20

Correct!