At what rate per cent per annum will the simple interest on a sum of money be $\frac{2}{5}$ of the principal in $10$ $years$?

$A$ person lent ₹ $10000$ to $B$ for $3$ $years$ and ₹ $6000$ to $C$ for $4$ $years$ on simple interest at the same rate of interest and received ₹ $5400$ in all from both of them as interest. What is the rate of interest (in $\%$)?

If the simple interest on a certain sum of money is ₹ $256$ and the rate of interest per annum equals the number of years,then the rate of interest (in $\%$) is:

Albert invested an amount of $x$ rupees in a fixed deposit scheme offering $10 \%$ per annum for the $1^{\text{st}}$ year and $15 \%$ per annum for the $2^{\text{nd}}$ year and received an amount of ₹ $20,240$ after two years. What is $x$ (in ₹)?

Two equal sums were lent at simple interest for $4$ years and for $3$ years respectively. The rate of interest in the latter case was $3 \%$ higher than that of the former case,but the amount in each was $Rs. 1088$. Find the rate of interest (in $\%$) of the former case?

How many years will it take for an amount of $Rs. 600$ to yield $Rs. 120$ as interest at $10 \%$ per annum of $S.I.$?