To determine who spent more time writing per problem, we need to calculate the writing time per problem for both Sonia and Maryna.
Sonia's Writing Time Per Problem:
- For 6 problems: 120 minutes → \( \frac{120 \text{ minutes}}{6 \text{ problems}} = 20 \text{ minutes/problem} \)
- For 18 problems: 360 minutes → \( \frac{360 \text{ minutes}}{18 \text{ problems}} = 20 \text{ minutes/problem} \)
- For 25 problems: 500 minutes → \( \frac{500 \text{ minutes}}{25 \text{ problems}} = 20 \text{ minutes/problem} \)
- For 60 problems: 1,200 minutes → \( \frac{1,200 \text{ minutes}}{60 \text{ problems}} = 20 \text{ minutes/problem} \)
Maryna's Writing Time Per Problem:
- For 8 problems: 200 minutes → \( \frac{200 \text{ minutes}}{8 \text{ problems}} = 25 \text{ minutes/problem} \)
- For 15 problems: 375 minutes → \( \frac{375 \text{ minutes}}{15 \text{ problems}} = 25 \text{ minutes/problem} \)
- For 20 problems: 500 minutes → \( \frac{500 \text{ minutes}}{20 \text{ problems}} = 25 \text{ minutes/problem} \)
- For 50 problems: 1,250 minutes → \( \frac{1,250 \text{ minutes}}{50 \text{ problems}} = 25 \text{ minutes/problem} \)
Conclusion:
- Sonia spent 20 minutes per problem.
- Maryna spent 25 minutes per problem.
Thus, Maryna spent more time writing per problem at the unit rate of 25 min. 1 problem.
So the correct answer is:
Maryna spent more time writing per problem at the unit rate of 25 min. 1 problem.