# SOLUTION: A stream Flows at a rate of 5 mph. A boat travels 75 mi upstream and returns in a total of 8 hours. What is the speed of the boat in still water?

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A stream Flows at a rate of 5 mph. A boat travels 75 mi upstream and returns in a total of 8 hours. What is the speed of the boat in still water?      Log On

 Ad: You enter your algebra equation or inequality - Algebrator solves it step-by-step while providing clear explanations. Free on-line demo . Ad: Mathway solves algebra homework problems with step-by-step help! Ad: Algebrator™ solves your algebra problems and provides step-by-step explanations!

 Linear Solvers Practice Answers archive Word Problems Lessons In depth

 Click here to see ALL problems on Linear Equations And Systems Word Problems Question 172429: A stream Flows at a rate of 5 mph. A boat travels 75 mi upstream and returns in a total of 8 hours. What is the speed of the boat in still water?Answer by ankor@dixie-net.com(16524)   (Show Source): You can put this solution on YOUR website!A stream Flows at a rate of 5 mph. A boat travels 75 mi upstream and returns in a total of 8 hours. What is the speed of the boat in still water? : Let s = boat speed in still water then (s-5) = speed upstream and (s+5) = speed down stream : Write a time equation: Time= : Time upstream + time downstream = 8 hours + = 8 : Multiply equation by (s-5)(s+5) (s-5)(s+5)* + (s-5)(s+5)* = 8(s-5)(s+5) results 75(s+5) + 75(s-5) = 8(s^2 - 25) : 75s + 375 + 75s - 375 = 8s^2 - 200 : 150s = 8s^2 - 200 : Arrange as a quadratic equation 8s^2 - 150s - 200 = 0 : Simplify divide equation by 2: 4s^2 - 75s - 100 = 0 Factors to: (4s + 5)(s - 20) = 0 Positive solution: s = +20 speed of boat in still water : : Check the solution by finding the times of up and down streams 75/15 = 5 hrs 75/25 = 3 hrs ------------- total = 8 hrs