The rate of interest is the percentage at which interest is calculated on the principal amount annually. It is usually represented as a percentage and can greatly affect the total interest earned or paid over time. In the problem, the rate of interest is given as 9% per annum.
This means that for every Rs 100 of the principal amount, Rs 9 is the interest earned per year, assuming a full year passes. It is crucial because:
- A higher rate of interest means more earnings from the same principal amount.
- The rate, although provided annually, needs adjustment if the time period is less than a year, like the 219 days in Karthik’s deposit.
Thus, understanding the rate of interest helps in accurately determining how much a deposit or loan will grow over a specified time period.