(1) Simple interest problem: principal × interest rate× term = interest;
Principal ×( 1+ interest rate× term) = principal and interest;
Principal and interest and cash (1+ interest rate × term) = principal.
Annual interest rate ÷ 12= monthly interest rate;
Monthly interest rate × 12= annual interest rate.
(2) Compound interest: principal ×( 1+ interest rate) deposit periods = sum of principal and interest.
For example, "someone deposits 2400 yuan with a term of 3 years, and the monthly interest rate is 10.2‰ (that is, monthly interest 1.02). After three years, how much is the principal and interest? "
Solution (1) is calculated at the monthly interest rate.
3 years = 65438+2 months ×3=36 months
2400×( 1+ 10.2%×36)
=2400× 1.3672
=328 1.28 (yuan)
(2) Use the annual interest rate.
Change the monthly interest rate to the annual interest rate first:
10.2‰× 12= 12.24%
Seek principal and interest again:
2400×( 1+ 12.24%×3)
=2400× 1.3672
=328 1.28 yuan (omitted)