Problema Solution
Ira leaves his dock and sails 36 mi upstream in 1.5 hr. It takes him only 1 hr to return to his dock. What was the speed of the current? What was the speed of Ira's boat in still water?
Answer provided by our tutors
let
d = 36 mi the distance traveled in one direction
t1 = 1.5 hr the time of the trip upstream
t2 = 1 hr the time of the trip downstream
s = the speed of the stream
v = the speed of the boat in still water
the speed of the boat upstream is: v - s
the speed of the boat downstream is: v + s
traveling upstream
(v - s)*t1 = d
(v - s)*1.5 = 36
traveling downstream
(v + s)*t2 = d
(v + s)*1 = 36
by solving the system of equations
(v - s)*1.5 = 36
v + s = 36
we find
s = 6 mph
v = 30 mph
click here to see the step by step solution of the system of equations
the speed of Ira's boat in still water was 30 miles per hour.