Question

a fisherman travels 9mi downstream with the current in the same time he travels 3 mi upstream against the current. if the speed of the current is 5mph what is the speed at which the fisherman travels in still water

Answer 1

Answer:

10 mph

Step-by-step explanation:

speed of boat in still water = x

speed of current = 5

speed of boat with current (downstream) = x + 5

speed of boat against current (upstream) = x - 5

distance downstream = 9

distance upstream = 3

time = t

speed = distance/time

distance = speed × time

downstream:

9 = (x + 5)t

upstream:

3 = (x - 5)t

9 = xt + 5t

3 = xt - 5t

9 = xt + 5t

-3 = -xt + 5t

-----------------

6 = 10t

t = 0.6

9 = (x + 5)0.6

15 = x + 5

x = 10