# math

The speed of a river current is 4 mph. IF a boat travels 20 miles downstream in the same time that it takes to travel 10 miles upstream, find the speed of the boat in still water.

1. 👍
2. 👎
3. 👁
1. downstream speed = u + 4
upstream speed = u - 4

20 = (u+4) t
10 = (u-4)t

so
20/(u+4) = 10/(u-4)

10 u + 40 = 20 u - 80

10 u = 120
u = 12 miles/hr

1. 👍
2. 👎

## Similar Questions

1. ### Algebra

The speed of the current is 7 mph. The boat travels three times slower against the current than with the current. What is the speed of the boat in still water? Plz answer as soon as possible!

2. ### Algebra

The current of a river moves at 3 miles per hour. It takes a boat 3 hours to travel 12 miles upstream, against the current, and return the same distance traveling downstream, with the current. What is the boats rate in still

3. ### algebra 1

a bout travels 280 miles downstream and back. The trip downstream took seven hours. The trip back took 14 hours. The speed of the boat in still water and the speed of the current

4. ### algabre

the speed of the current in a river is 6 mph a ferry operator who works that part of the river is looking to buy a new boat for his business everyday his route takes him 22.5 miles against the current and back to his deck and he

1. ### Math

A boat travels 45 miles upstream in 5h. The boat travels the same distance downstream in 3hr. What is the rate of the boat in still water? What is the rate of the current? (thank you)

2. ### elem algebra

the current in a stream moves at a speed of 10 mph. a boat travels 17 mi upstream and 17 mi downstream in a total time of 10 hr. What is the speed of the boat in still water?

3. ### Physics

A boat crosses a river of width 122 m in which the current has a uniform speed of 2.39 m/s. The pilot maintains a bearing (i.e., the direction in which the boat points) perpendicular to the river and a throttle setting to give a

4. ### physics

your boat departs from the bank of a river that has a swift current parallel to its banks. if you want to cross the river in the shortest amount of time, you should direct your boat a.) perpendicular to the current b.) upstream

1. ### algebra

Traveling downstream a certain boat went 21 mph. Traveling upstream it went only 5 mph. Find the speed of the boat in still water and the speed of the current.

2. ### Science

A boat moves at a speed of 15 km/h in still water. The river it is traveling in flows at a rate of 3 km/h downstream. What is the velocity of the boat if it travels downstream? What is the velocity of the boat if it travels

3. ### physics

A boat travels at 3.8 m/s and heads straight across a river 240 m wide. The river flows at 1.6 m/s. Find A) The boat's resultant velocity. B) How long it takes the boat to cross the river. C) How far downstream the boat is when it

4. ### Algebra 2

The excursion boat on the river takes 2½ hours to make the trip to a point 12 miles upstream and to return. If the rate at which the boat travels in still water is 5 times the rate of the river current, what is the rate of the