The interest that is calculated uniformly on a sum of money is called simple interest (SI). Principal is the money borrowed or lent out for certain period is called the principal / sum. Interest is the extra money paid for using other money.
Usually, the following denotations are used:-
Principal = P
Rate of Interest = r % per annum (p.a.)
Time = t years
The, formula for Simple Interest is given by:-
Simple Interest (SI) = (P×r×t)) /100
Also, Amount (A) = SI + P.