Final answer:
The annual return on investment (ROI) for buying an investment at $800 and selling it for $1,000 ten months later is 30%.
Step-by-step explanation:
To calculate the annual return on investment (ROI), we must first determine the overall return, then annualize it. You bought an investment for $800 and sold it for $1,000, resulting in a gain of $200. Since the investment was held for 10 months, we need to convert the return to an annual figure. The formula for the annual ROI is (Profit/Cost of Investment) x (12/Number of Months) x 100, which in this case is ($200/$800) x (12/10) x 100 = 30% annual ROI.