3. For a children's party, pastries were prepared: 10 eclairs, 20 mini tarts, 30 chocolate brownies, 40 cream puffs. What is the maximum number of children who can each take three different pastries?
Answer: 30.

Solution: From eclairs, baskets, and brownies, at least 2 pastries must be taken, and there are 60 of them in total, meaning no more than 30 children can take three different pastries. They can do this as follows: 10 children will take an eclair, a brownie, and a roll, and 20 children will take a basket, a brownie, and a roll.

Comment: Correct solution - 20 points. Proof that 30 is the maximum value - 10 points, example - 10 points. If the proof is insufficiently justified, 5 points are deducted. Solution started, with some progress - 5 points. Solution started, but no significant progress - 1 point. Correct answer given without explanation - 0 points.