Which option is not a standard method of calculating interest?

• A. Simple interest
• B. Compound interest
• C. Continuously compounded interest
• D. Binary interest

Answer: (D)

Understanding how interest grows relies on the idea of compounding or not, and how often it is applied. Simple interest earns interest only on the original principal, so the amount grows linearly with time. Compound interest with periodic reinvestment earns interest on both the principal and accumulated interest, giving the familiar growth factor (1 + r/n)^(nt). When compounding happens continuously, the growth follows the exponential form A = P e^(rt), representing the theoretical limit as the compounding frequency increases without bound. The term described as binary interest isn’t a standard method in financial math; there isn’t a widely used formula or interpretation for “binary” growth in this context. The other methods—simple, periodic compound, and continuous compound—are well established and taught because they describe real, widely used ways money can accumulate over time.