[Again with the long inhales. God knows what kind of weird respiratory situation this guy's got.]

You have a number of round, buoyant fruit. Eighty-one of them. They all exert the same amount of lift except for one, which is more buoyant. It's over-ripe and you don't want it.

You have a set of inverted scales. How few times can you use them to find the over-ripe fruit? Smallest number possible, please.

[It's really just an inversion of a fairly common puzzle, using lift instead of weight. He'll see if Layton can solve it.]