SOLUTION: A motorboat travels 648km in 9 hours going upstream and 588km in 6 hours going downstream. What is the speed of the boat in still water, and what is the speed of the current?
Question 176740: A motorboat travels 648km in 9 hours going upstream and 588km in 6 hours going downstream. What is the speed of the boat in still water, and what is the speed of the current?
You can put this solution on YOUR website! A motorboat travels 648km in 9 hours going upstream and 588km in 6 hours going downstream. What is the speed of the boat in still water, and what is the speed of the current?
;
let x = boat speed in still water
let y = speed of the current
then
(x-y) = boat speed upstream
and
(x+y) = boat speed downstream
;
write a distance equation for each trip; (dist = time*speed)
9(x-y) = 648
6(x+y) = 588
;
simplify both equations, divide the 1st one by 9 and the 2nd one by 6:
x - y = 72
x + y = 98
--------------addition eliminates y; find x
2x = 170
x =
x = 85 km/hr boat speed in still water
;
Find y using eq: x + y = 98
85 + y = 98
y = 98 - 85
y = 13 km/hr is the current
:
:
check solutions in 1st original equation
9(x-y) = 648
9(85 - 13) = 648
9(72) = 648; confirms our solutions
