$A$ certain sum becomes ₹ $1020$ in $5$ years and ₹ $1200$ in $8$ years at simple interest. What is the value of Principal (in ₹)?

The simple interest on a sum for $8$ years is ₹ $47500$. The rate of interest is $10 \%$ per annum for the first $5$ years and $15 \%$ per annum for the next $3$ years. What is the value (in ₹) of the sum?

$A$ certain sum becomes $5$ times in $3$ years at simple interest. In how many years will it become $13$ times?

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

If ₹ $1000$ is invested at an interest rate of $5 \%$ and the interest is added to the principal every $10$ years,then the number of years in which it will amount to ₹ $2000$ is:

$A$ part of $Rs. 38800$ is lent out at $72 \%$ per annum for six months. The rest of the amount is lent out at $5 \%$ per annum after one year. The ratio of interest after $3$ years from the time when the first amount was lent out is $5: 4$. Find the second part that was lent out at $5 \%$ (in $Rs.$).