Elementary math at OCC

Question

A motorboat travels 160

 kilometers in 4

 hours going upstream. It travels 240

 kilometers going downstream in the same amount of time. What is the rate of the boat in still water and what is the rate of the current? 

Answer 1

160/4 = 240/x = 40 d/r = t, distance/speed = time

40x = 240,

x=5 km per hour downstream = still water speed plus current speed, x=w+1

current = 1 mph

speed in still water = 5 kph

160/(5-1)) = 240/(5+1)

160/w-c = 240/(w+c)

2/(w-c) = 3/(w+c)

2(w+c) = 3(w-c)

2w +2c = 3w- 3c

w = 5c

w= 5kph, c= 1 kph