@899d9141 After looking up and seeing why it's impossible, I took the reasoning to calculate what the you get going at the intuitive answer of 45mph in the last mile. Got 22.5mph for whole trip. So going 15mph for a mile and then 45mph for a mile gives you "average" speed of 22.5mph. I feel like there are some high school math text books out there that are proper fucked on this one...