Kermit, maybe there are two mindsets at work here, the way mine and yours and maybe Einstein's worked, and the way Max Wertheimer's and maybe the author's of the article works :)

I couldn't work it out either, until I thought about two cars, driving in a race, both starting at the same time, one doing 30 mph all the way, and the other only doing 15 mph for the first mile. At the same time as the car doing 15 mph gets to the one mile mark, the car doing 30mph is crossing the 2 mile finishing line, so the slower car has lost all chance of ever catching up. Does that make more sense to you?

The psychological trick is the hill, it tempts us to expect the downhill slope will compensate for the time it took to climb the hill, we just don't realise that solving the riddle has nothing to do with the hill, and actually it has no solution :)