Applications
9-6Wind and Water Current Problems
Overview
With wind or current, effective speed = own speed ± current. Use d = rt for both directions.
Key ideas
- Downstream: rate + current.
- Upstream: rate − current.
- Use two equations from the two trips.
Worked examples
Example 1
Problem. A boat goes 30 mi downstream in 2 h and 30 mi upstream in 5 h. Find boat speed and current.
Solution. b + c = 15, b − c = 6 → b = 10.5, c = 4.5.
Practice
Try each one. Click Show answer when ready.
- 1.
Plane: 600 mi with wind in 2 h, against in 3 h. Find speed and wind.
- 2.
Boat: 24 mi downstream in 2 h, upstream in 6 h. Find speed and current.
- 3.
Plane with wind: 8 h covers 1600 mi; against, 10 h. Find speed and wind.
Challenge problems
A little tougher — great for test prep. Click Show answer when ready.
- 1.
A boat travels 24 miles downstream in 2 hours and 18 miles upstream in 3 hours. Find the speed of the boat and the current.
- 2.
An airplane flies 600 miles with the wind in 2 hours and 480 miles against the wind in 3 hours. Find the plane's speed and wind speed.