Question

Marco can paddle his canoe at a rate of 6 miles per hour on unmoving water. However, today Marco is canoeing down (with the current), and then back up (against the current), a river that's moving at a rate of 1 mile per hour, so the current affects his rate of speed. If it takes Marco 6 total hours to go x miles downstream and then return to his starting point, how far downstream does he travel?
A) 1.25 miles
B) 2.5 miles
C) 5 miles
D) 17.5 miles

Answer 1

Answer:

S = v1 t1 = 7 t1    traveling downstream

S = v2 t2 = 5 t2    traveling upstream

7 t1 = 5 t2

7 (6 - t2) = 5 t2     since t1 + t2 = 6

42 - 7 t2 = 5 t2

t2 = 42 / 12 = 3.5 hrs so t1 = 2.5 hrs

S = 7 t1 = 7 * 2.5 = 17.5 mi

Also, S = 5 t2 = 5 * 3.5 = 17.5 mi