Justin recently drove to visit his parents who live 96 miles away. On his way there his average speed was 20 miles per hour faster than on his way home (he ran into some bad weather). If Justin spent a total of 4 hours driving, find the two rates.

Answer 1

[96 / (r + 20)] + (96 / r) = 4

24 r + 24(r + 20) = r(r + 20)

r^2 - 28 r - 480 = 0 ... factoring ... (r - 40)(r + 12) = 0