SOLUTION: 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 t

Algebra ->  Customizable Word Problem Solvers  -> Numbers -> SOLUTION: 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 t      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 442300: 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?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
against current x- 70.00 hours
with current x+ 10.00 hours

Distance = same=210
Boat speed =x
current speed =y
t=d/r
210/(x-y)=70.00
70(x-y)=210.00
70x-70y =210 ....................1
210/(x+y)=10.00
10.00(x +y)=210
10.00x+10.00y=210 ...............2
Multiply (1) by 1.00
Multiply (2) by 7.00
we get
70x-70y=210
70x+70y=1470
140x=1680
/140
x =12 mph Boat speed
plug value of x in (1)
70x-70y=210
840-70y=210
-70y=210-840
-70y=-630
y=9 mph current speed