SOLUTION: please help me solve this problem in quadratic equation;
1.a motorboat takes 4 hours to travel 30 miles downstream and then 18 miles upstream on a river whose current flows at the
Algebra.Com
Question 154461: please help me solve this problem in quadratic equation;
1.a motorboat takes 4 hours to travel 30 miles downstream and then 18 miles upstream on a river whose current flows at the rate of 3 miles per hour. How fast can the boat travel in still water?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
1.a motorboat takes 4 hours to travel 30 miles downstream and then 18 miles upstream on a river whose current flows at the rate of 3 miles per hour. How fast can the boat travel in still water?
Let "b" be the speed of the boat in still water.
--------------
Upstream DATA:
distance = 18 miles ; rate = b-3 ; time = d/r = 18/(b-3) hrs.
-----------------
Downstream DATA:
distance = 30 miles ; rate = b+3 ; time = d/r = 30/(b+3) hrs
===============================================
EQUATION:
time up + time down = 4 hrs
18/(b-3) + 30/(b+3) = 4
18(b+3) + 30(b-3) = 4(b^2-9)
18b + 54 + 30b - 90 = 4b^2 - 36
4b^2 - 48b = 0
b^2 - 12 = 0
Positive solution:
b = sqrt(12) = 3.464 mph (speed of the boat in still water)
==============
Cheers,
Stan H.
RELATED QUESTIONS
please help me solve this problem in quadratic equation;
48.A rectangular plot of ground (answered by ankor@dixie-net.com)
Please help me solve this problem:
A motorboat can go 14 miles downstream on a river... (answered by mananth)
A motorboat takes 4 hours to travel 192 miles going upstream. The return trip takes 2... (answered by mananth)
A motorboat takes 5 hours to travel 200 miles going upstream. The return trip takes 4... (answered by josgarithmetic)
Can you help me set up a rational equation to solve this word problem algebraically... (answered by josmiceli)
Can you help me set up a rational equation to solve this word problem algebraically... (answered by josgarithmetic,MathTherapy)
I need HELP!!! Can you please help me???
Solve by writing a system of equations.
It... (answered by ankor@dixie-net.com)
Determine the speed of a motorboat in still water and the speed of the river current, if... (answered by scott8148)
please help me solve this problem : a boat takes 45 minutes to get 6 miles downstream (answered by mananth)