Answer:
Here is a QBasic expression for calculating SI (Simple Interest) using PTR (Principal, Time, and Rate):
SI = (PTR / 100)
In this expression, PTR represents the product of the principal amount, time period, and rate of interest. The division by 100 is necessary because the formula for simple interest uses a percentage rate, while mathematical expressions typically use decimal values.
To use this expression in a program, you would need to assign values to the variables P, T, and R representing the principal, time period, and interest rate respectively. Then you could calculate the simple interest using the above expression:
SI = (P * T * R) / 100
This expression would give you the value of the simple interest based on the given values of principal, time period, and interest rate.