You could find the distance first v = 12 mph t = 20 minutes = 20/60 = 1/3 of an hour d = r * t d = 12 * 1/3 = 4 miles.
And put that distance into Jim's time d = 4 miles r = ??? t = 15 minutes = 15/60 = 1/4 hour r = d/t r = 4/0.25 = 16 mph. I wish I could bike that quickly.
There is another way to do it more directly. The distance is the same for both of them. r*t = R*T R Jim's speed and r is jen's speed. 12 * 1/3 = R * 1/4 Multiply both sides by 4 12 * 1/3 * 4 = R Cancel 12 and 1/3 R = 16.
