5. Private Petrov took a bucket of unpeeled potatoes and cleaned them in 1 hour. In the process, $25 \%$ of the potatoes went into peels. How long did it take for him to have half a bucket of peeled potatoes?
Answer. In 40 minutes.

Solution. Since a quarter of the potatoes went into peels, Petrov received three quarters of a bucket of peeled potatoes in 1 hour. This means that a quarter of a bucket of peeled potatoes Petrov received in 20 minutes, and half a bucket - in 40 minutes.

## Grading Criteria.

- Correct solution - 7 points.
- Correct approach, but an arithmetic error at the end of the solution (the answer should still be reasonable, not 1 hour or 10 minutes) - 5 points.
- Correct reasoning - up to 2 points.
- Only the answer $-\mathbf{1}$ point.