The simple interest on a certain sum at $4 \%$ per annum for $2$ years is ₹ $80$. The compound interest (in ₹) on the same sum for the same period is

The sum for $2$ years gives a compound interest of ₹ $3225$ at the rate of $15 \%$ per annum. The principal amount is (in ₹):

If the compound interest on a certain sum for $2$ years is ₹ $60.60$ and the simple interest is ₹ $60$,then the rate of interest per annum (in $\%$) is

An amount of money at compound interest grows up to ₹ $3,840$ in $4$ years and up to ₹ $3,936$ in $5$ years. Find the rate of interest (in $\%$).

$A$ tree increases annually by $\frac{1}{8}$ of its height. By how much will it increase (in $cm$) after $2$ years,if it stands today $64 \ cm$ high?

On a sum of money,the simple interest for $2$ years is ₹ $660$,while the compound interest is ₹ $696.30$,the rate of interest being the same in both the cases. The rate of interest (in $\%$) is