Step 1: Identify the given values. The bill amount (Principal) is Rs. 12000, the bankers' discount (BD) is Rs. 900, and the time (in years) is 9 months.
Step 2: Convert the time from months to years. Since 9 months is equal to 0.75 years (9/12 = 0.75).
Step 3: Use the formula for rate of interest: Rate = (BD × 100) / (Principal × Time).
Step 4: Substitute the values into the formula: Rate = (900 × 100) / (12000 × 0.75).
Step 5: Calculate the denominator: 12000 × 0.75 = 9000.
Step 6: Now calculate the rate: Rate = (900 × 100) / 9000.
