What will be $C.I.$ (in $Rs.$) on an amount of $Rs. 10000$ at the rate of $20$ $p.c.p.a.$ in two years if the interest rate is compounded half-yearly?

The compound interest accrued on an amount at the end of $3$ $years$ at $15$ $p.c.p.a.$ is $Rs. 6500.52$. What is the principal amount (in $Rs.$)?

$A$ sum of money invested at compound interest amounts to ₹ $800$ in $3$ years and to ₹ $840$ in $4$ years. The rate of interest (in $\%$) per annum is

$A$ man borrows ₹ $3825$ to be paid back with compound interest at the rate of $4 \%$ per annum by the end of $2$ years in two equal yearly instalments. How much will be each instalment (in ₹)?

If a sum of money placed at compound interest,compounded annually,doubles itself in $5$ years,then the same amount of money will be $8$ times of itself in how many years?

If the compound interest on a sum for $2$ years at $12 \frac{1}{2} \%$ per annum is ₹ $510$,the simple interest (in ₹) on the same sum at the same rate for the same period of time is