Rational Expressions

Question

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

Answer 1

Let x be the speed of the boat in km/h

x + 6km/h = 94

x - 6km/h = 47

94/47 = 2 so we can say

x + 6km/h = 2(x - 6km/h)

x + 6km/h = 2x -12 km/h

x - 2x km/h = -12 km/h - 6km/h

-x = -18 km/h

or

x = 18 km/h

Hence, the speed of the boat in still water is 18km/h