1. The problem asks for the formula to find simple interest. 2. The formula for simple interest is: $$I = Prt$$ where: - $I$ is the interest earned, - $P$ is the principal amount (initial investment), - $r$ is the annual interest rate (in decimal), - $t$ is the time the money is invested for (in years). 3. Important rules: - The interest rate $r$ must be converted from a percentage to a decimal by dividing by 100. - The time $t$ must be in years; if given in months, convert by dividing by 12. 4. Explanation of options: - Option A: $I = Prt$ is the correct simple interest formula. - Option B: $I = P(1+r)^t$ is the formula for compound interest amount, not simple interest. - Option C: $I = F - P$ is the formula for interest when final amount $F$ and principal $P$ are known, but it is not the direct formula for simple interest. - Option D: $I = \frac{F}{(1+r)^t}$ is incorrect for simple interest. Final answer: Option A. $I = Prt$