Final answer:
To find the interest rate, use the formula for simple interest: Interest = Principal x Rate x Time. In this case, the interest rate is approximately 11.67%.
Step-by-step explanation:
To find the interest rate, we can use the formula for simple interest: Interest = Principal x Rate x Time. In this case, the principal is Rs 18,000, the interest is Rs 1,850, and the time is 90 days. Plugging in these values, we have: Rs 1,850 = Rs 18,000 x Rate x (90/365). Solving for the interest rate, we find that it is approximately 0.1167, or 11.67%.