7.3. While Cheburashka eats two portions of ice cream, Winnie-the-Pooh manages to eat five such portions, and while Winnie-the-Pooh eats three portions, Karlson eats seven. Working together, Cheburashka and Karlson ate 82 portions. How many portions did Winnie-the-Pooh eat during this time? Justify your answer.
Solution: Suppose Winnie-the-Pooh ate exactly 15 portions of ice cream. Since $15=3 \cdot 5$, Cheburashka ate $3 \cdot 2=6$ portions, and Karlson ate $-5 \cdot 7=35$ portions. Together, Karlson and Cheburashka ate $6+35=41$ portions, which is half of the 82 portions given in the problem. Therefore, the feast actually lasted twice as long as assumed, and each participant ate twice as much ice cream. In particular, Winnie-the-Pooh ate $15 \cdot 2=30$ portions.

Answer: 30 portions.

Recommendations for checking:

| is in the work | points |
| :--- | :--- |
| Correct and justified answer | 7 points |
| The answer is incorrect due to an arithmetic error, but the approach is correct | 6 points |
| Correctly found the ratio of the number of portions that Winnie-the-Pooh, Karlson, and Cheburashka eat in the same amount of time | 3 points |
| Correct answer without justification or with incorrect justification | 1 point |