The difference between the compound interest and the simple interest accrued on an amount of ₹ $18000$ in $2$ years was ₹ $405$. What was the rate of interest per cent per annum?

Find the least number of complete years in which a sum of money put out at $20 \%$ compound interest will be more than double?

If the difference between the $C.I.$ compounded half-yearly and simple interest on a sum at $10 \%$ per annum for one year is $Rs. 25$,the sum (in $Rs.$) is:

In what time (in $years$) will ₹ $8,000$ at $3 \%$ per annum produce the same interest as ₹ $6,000$ does in $5$ years at $4 \%$ simple interest?

The difference between the compound interest and the simple interest on ₹ $8000$ for $3$ years at $5 \%$ per annum is (in ₹):

$A$ certain sum of money (in $Rs.$) gives $Rs. 500$ as Simple Interest $(S.I.)$ at $5 \%$ per annum for $1$ year. What is the Compound Interest $(C.I.)$ on the same sum at the same rate at the end of $2$ years?