# A boat traveled 210 miles downstream and back. The trip downstream took 10 hours The trip back took 70 hours. What is the speed of the boat in still water? What is the speed of the current?

##### 2 Answers

#### Answer:

The speed of boat in still water is

#### Explanation:

As boat travelled

And as it travelled

Let the speed of boat in still water be

As such speed down stream would be

Adding the two

Hence, the speed of boat in still water is

#### Answer:

The speed of the boat in still water is 12 miles per hour.

The speed of the current is 9 miles per hour.

#### Explanation:

Let

Let

When traveling downstream, the speed of the boat is "helped" by the speed of the current and the net speed is

When traveling upstream, the current opposes the movement of the boat, and net speed is

Set up a table where

Downstream

Upstream

Recall that distance = rate x time or

*Equation from downstream information*

*Equation from upstream information*

*Distribute*

*Multiply the 1st equation by 7*

*Add the 1st equation to the 2nd*

*Divide both sides by 140*

*Subsitute x=12 into one of the original* *equations to find c*

The speed of the boat is 12 miles per hour.

The speed of the current is 9 miles per hour.