$A$ lent ₹ $6000$ to $B$ for $2$ $years$ and ₹ $1500$ to $C$ for $4$ $years$ and received altogether from both ₹ $900$ as simple interest. The rate of interest is (in $\%$):

In simple interest rate per annum,a certain sum amounts to ₹ $5,182$ in $2$ $years$ and ₹ $5,832$ in $3$ $years$. The principal in rupees is:

$A$ sum of ₹ $16800$ is divided into two parts. One part is lent at a simple interest rate of $6 \%$ per annum and the other at $8 \%$ per annum. After $2$ years,the total amount received is ₹ $19000$. The sum lent at the rate of $6 \%$ simple interest (in ₹) is:

The simple interest on a sum of money is $\frac{1}{9}$ of the principal and the number of years is equal to the rate per cent per annum. The rate per cent per annum is equal to

At what rate per cent per annum will a sum of money double in $16$ years (in $.25$)?

$A$ sum of money lent out at simple interest amounts to $Rs. 720$ after $2$ years and $Rs. 1020$ after a further period of $5$ years. Find the principal (in $Rs.$).