1. The problem is to perform calculations using the BA II Plus calculator and ensure every decimal is calculated precisely. 2. The BA II Plus calculator is a financial calculator that allows precise decimal calculations. 3. To calculate every last decimal, use the calculator's full precision mode and avoid rounding intermediate results. 4. For example, if calculating $\frac{123.456}{7.89}$, enter the exact numbers and perform the division. 5. The calculator will display the result with full decimal precision, such as $15.6405063291$. 6. Always keep intermediate results displayed or stored to avoid rounding errors. 7. When writing answers, include all decimals shown by the calculator unless instructed otherwise. 8. This method ensures accuracy and precision in financial and mathematical calculations.