To use the simple interest formula we substitute in the values for variables that are given and then solve for the unknown variable. Simple interest does not add any interest rate on the interest amount gathered on the principal amount. It is calculated on the principal amount.
Where r is in decimal form.
The simple interest formula is the product of the principal amount P P rate of interest r r and time T T in year. When the amount of interest the principal and the time period are known you can use the derived formula from the simple interest formula to determine the rate as follows. To use the simple interest formula we substitute in the values for variables that are given and then solve for the unknown variable. An amortization schedule is a table with the details of the amount of each payment allocated to principal and interest.