1. **State the problem:** Mr. Shi Zu borrowed 90780 and paid 750 interest after 2 months. We need to find the interest rate. 2. **Formula used:** The simple interest formula is: $$I = P \times r \times t$$ where: - $I$ is the interest, - $P$ is the principal (amount borrowed), - $r$ is the interest rate per year (in decimal), - $t$ is the time in years. 3. **Convert time to years:** Since 2 months is $\frac{2}{12} = \frac{1}{6}$ years, we have: $$t = \frac{1}{6}$$ 4. **Substitute known values:** $$750 = 90780 \times r \times \frac{1}{6}$$ 5. **Solve for $r$:** Multiply both sides by 6: $$750 \times 6 = 90780 \times r$$ $$4500 = 90780 \times r$$ Divide both sides by 90780: $$r = \frac{4500}{90780}$$ 6. **Calculate $r$:** $$r \approx 0.04956$$ 7. **Convert to percentage:** $$r \times 100 \approx 4.956\%$$ **Final answer:** The interest rate is approximately **4.96% per year**.