comfort-shattering maths

I have a friend with a black-and-white brain (says he), who wouldn't let anybody get away with bad science. He send me this: So now I stand corrected: Running out of the rain WILL get you less wet then just walking. How sad. I liked the counter-intuitive feel, the idea that in some cases doing nothing special would help more then hectic moving, that staying in could be better then moving out. But no.
Plus I'll never know if it was just one more case of Infamous Selective Remembering, or if the book had it wrong. (Me being me, odds are it's ISR. Very prone I am.)