$A$ sum of ₹ $8000$ is divided into two parts. The simple interest on the first part at the rate of $21 \%$ per annum is equal to the simple interest on the second part at the rate of $35 \%$ per annum. What is the interest (in ₹) of each part?

Sapna borrowed a certain sum of money from Kavita under the following repayment scheme based on simple interest: $8 \%$ $p.a.$ for the initial $2$ $years$,$9.5 \%$ $p.a.$ for the next $4$ $years$,$11 \%$ $p.a.$ for the next $2$ $years$,and $12 \%$ $p.a.$ after the first $8$ $years$. Find the total amount (in $Rs.$) which a sum of $Rs. 9000$ taken for $12$ $years$ becomes at the end of $12$ $years$.

In what time will ₹ $8100$ produce the same income at $3 \%$ as ₹ $225$ in $4$ years at $3 \%$?

$A$ man invests a certain sum of money at $6 \%$ $p.a.$ simple interest and another sum at $7 \%$ $p.a.$ simple interest. His income from interest after $2$ $years$ was $Rs. 354$. One-fourth of the first sum is equal to one-fifth of the second sum. Find the total sum (in $Rs.$) he invested.

Adam borrowed some money at the rate of $6 \% \text{ p.a.}$ for the first two years,at the rate of $9 \% \text{ p.a.}$ for the next three years,and at the rate of $14 \% \text{ p.a.}$ for the period beyond five years. If he pays a total interest of ₹ $11,400$ at the end of nine years,how much money (in ₹) did he borrow?

The annual payment of $Rs. 160$ in $5 \, \text{years}$ at $5 \%$ per annum simple interest will discharge a debt of (in $Rs.$):