Subject: help!
Name: Kristy
Who are you: Student

Romo decided to make a 28km trip up and 28km trip down the Grand River. the speed of the current is 3km. one way Romo travelled with the current and the other way against the current. During his trip, Romo stopped for half an hour for lunch. if Romo's total trip lasted 6hours, how fast did he travel?


Hi Kristy.

Let R be Romo's speed relative to the water.
Let Ta be the time he spends paddling away from his starting point.
Let Tb be the time he spends paddling back towards his starting point.

It doesn't matter to the total time whether he paddles before lunch or after lunch (assuming he doesn't get a cramp), so let's just assume (mathematicians say "without loss of generalization") he travels against the current first.

Since distance equals time x speed, we can write:

28 = Ta (R-3)
28 = Tb (R+3)

and the total time is:

Ta + Tb + .5 = 6

Now you have three equations with three unknowns. Solve the first two for Ta and Tb , add them together and substitute into the third equation. Solve for R, your answer.

Hope this helps,
Stephen La Rocque.