Question

3). Sam rows up a river to camp in three hours. The next day he makes the return trip downstream in one hour. If he can row two mph in still water, how fast is the current?(The question was not answered last time).

Answer 1

let rate of current be x mph
distance upstream = 3(2-x)
distance downstream = 1(2+x)
but the two distances are the same

2+x = 3(2-x)
2+x = 6-3x
4x = 4
x = 1

check :
in both cases the distance is 3 miles
time to go 3 miles at 2-1 mph is 3 hours
time to go 3 miles at 2+1 mph is 1 hour