SOLUTION: A boat can travel at a speed of 12 km/h in still water. If it takes three hours to go 15 km upstream and back, find the speed of the current, giving your answer correct to 2 deci

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: A boat can travel at a speed of 12 km/h in still water. If it takes three hours to go 15 km upstream and back, find the speed of the current, giving your answer correct to 2 deci      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 754313: A boat can travel at a speed of 12 km/h in still water. If it takes three hours to go
15 km upstream and back, find the speed of the current, giving your answer
correct to 2 decimal places.
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
A boat can travel at a speed of 12 km/h in still water. If it takes three hours to go
15 km upstream and back, find the speed of the current, giving your answer
correct to 2 decimal places.
***
let x=speed of current
12+x =speed of boat downstream
12-x =speed of boat upstream
travel time=distance/speed
..
15%2F%2812%2Bx%29%2B15%2F%2812-x%29=3
LCD: (12+x)(12-x)
15%2812-x%29%2B15%2812%2Bx%29=3%28144-x%5E2%29
180-15x+180+15x=432-3x^2
3x^2-72=0
x^2-24=0
x^2=24
x=-√24 (reject, x>0)
or
x=√24≈4.90
speed of current≈4.90 km/h