Rational Expression

Question

The speed of a stream is 6 km/h. If a boat travels 94 km downstream in the same time that it takes to travel 47 km upstream, what is the speed of the boat in still water?

Answer 1

Let x = speed of the boat in still water

Speed downstream = x + 6 and speed upstream = x - 6

Distance = (Rate)(Time), so Time = Distance / Rate

Time upstream = Time downstream

So, 47 / (x - 6) = 94 / (x + 6)

47( x + 6) = 94(x - 6)

x + 6 = 2(x - 6)

x + 6 = 2x - 12

x = 18 kph