Puzzler #2

[ccb_v2 0]

Your friend measures your average while you shoot hoops (i.e. if you shot six times, made two shots, and missed four, then your average is 33.333%.) Near the beginning of the game, you're not doing very well, and your average is about 50%. Later on, the practice is starting to pay off and you get your average up to about 80%. The question is, just knowing this, can you tell for sure whether your average was ever exactly equal to 75%?By the way, "yes" or "no" doesn't cut it -- you could be just guessing. You have to explain why. I'll announce the winner whenever someone gets it right; then it's their turn to put up a new puzzle topic.