$A$ sum of money placed at compound interest doubles itself in $4$ $years$. In how many $years$ will it amount to four times itself?

$A$ certain sum of money at compound interest grows up to ₹ $12960$ in $2$ years and up to ₹ $13176$ in $3$ years. Find the rate per cent per annum.

If the amount is $6 \frac{1}{4}$ times the principal after $2$ years at compound interest,the rate of interest (in $\%$) per annum is

Sonika invested an amount of ₹ $5800$ for $2$ years. At what rate of compound interest (in $\% \text{ p.a.}$) will she get an amount of ₹ $594.50$ as interest at the end of two years?

Aditya invests $Rs. 50,000$ in a fixed deposit at $10 \%$ $C.I.$ for $2$ years. At the end of $2$ years,she puts the money in another deposit at $12 \%$ $S.I.$ for $3$ years. What was the final value (in $Rs.$) of the initial investment?

The simple interest accrued on a certain principal is ₹ $2,000$ in five years at the rate of $4$ percent $p.a.$ What would be the compound interest (in ₹) accrued on the same principal at the same rate in two years?