Simple interest: find the time

Use interest = principal × rate × time, with the rate as a percent per year.

1. $400 at 10% simple interest per year earns $80. For how many years was it invested?
2. $600 at 2% simple interest per year earns $36. For how many years was it invested?
3. $500 at 10% simple interest per year earns $150. For how many years was it invested?
4. $400 at 2% simple interest per year earns $24. For how many years was it invested?
5. $800 at 4% simple interest per year earns $64. For how many years was it invested?
6. $1800 at 2% simple interest per year earns $108. For how many years was it invested?
7. $1800 at 3% simple interest per year earns $54. For how many years was it invested?
8. $500 at 2% simple interest per year earns $30. For how many years was it invested?
9. $700 at 6% simple interest per year earns $42. For how many years was it invested?
10. $700 at 6% simple interest per year earns $126. For how many years was it invested?
11. $300 at 2% simple interest per year earns $12. For how many years was it invested?
12. $2500 at 3% simple interest per year earns $75. For how many years was it invested?
13. $4600 at 2% simple interest per year earns $460. For how many years was it invested?
14. $2300 at 5% simple interest per year earns $115. For how many years was it invested?
15. $2900 at 5% simple interest per year earns $870. For how many years was it invested?
16. $1000 at 6% simple interest per year earns $300. For how many years was it invested?
17. $7300 at 4% simple interest per year earns $584. For how many years was it invested?
18. $5000 at 4% simple interest per year earns $400. For how many years was it invested?
19. $8700 at 9% simple interest per year earns $6264. For how many years was it invested?
20. $2700 at 8% simple interest per year earns $1080. For how many years was it invested?