A word problem to find the current speed

Question

Sean can kayak 7 mph in still water. Sean can kayak 4 miles upstream in the same time that it takes him to kayak 10 miles downstream on Catamount Creek. What is the current speed of Catamount creek river?

Answer 1

So, if I row 7 mph in still water and I go downstream in a 3 mph current, I'm travelling 10 mph. Upstream I'd be going 4 mph.

d = rt, so t = d/r and the times are equal.

4/(7 - c) = 10/(7 + c)

Cross multiply!

4(7 + c) = 10(7 - c)

The rest is on you!