$A$ 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.

$A$ sum of $Rs. 8448$ is to be divided between $X$ and $Y$ who are respectively $18$ and $19 \,yr$ old,in such a way that if their shares be invested at $6.25 \%$ per annum at compound interest,they will receive equal amounts on attaining the age of $21 \,yr$. The present share of $X$ is (In $Rs.$)

If the compound interest on a certain sum for $3$ years at $5 \%$ p.a. exceeds the simple interest on the same sum for the same time and at the same rate by $Rs. 183$,find the sum (in $Rs.$).

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?

What will be the amount (in ₹) received on $25000$ at the rate of $20 \%$ per annum compounded yearly for $4$ years?

$A$ 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