$A$ 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

The difference between the compound interest and simple interest on a certain sum at $3 \%$ per annum for $3$ years is ₹ $27.27$. The sum is (in ₹):

$A$ man gave $50 \%$ of his savings of ₹ $84,100$ to his wife and divided the remaining sum among his two sons $A$ and $B$ of $15$ and $13$ years of age respectively. He divided it in such a way that each of his sons,when they attain the age of $18$ years,would receive the same amount at $5 \%$ compound interest per annum. The share of $B$ was (in ₹):

The compound interest on a sum of money for $3$ years at $5 \%$ per annum is ₹ $1324.05$. What is the simple interest (in ₹)?

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

Which information given below is sufficient to know the principal amount if the difference between the $C.I.$ and $S.I.$ for $2$ years is $18$?
$(I)$ The rate is same at which an amount of $Rs. 1000$ becomes $1120$ in $2$ years under $S.I.$
$(II)$ The principal is $Rs. 2000$.