$A$ certain sum of money amounts to ₹ $918$ in $2$ $years$ and ₹ $969$ in $3.5$ $years$ at simple interest. What is the rate of interest (in $\%$ $p.a.$)?

Prakash lends a part of ₹ $20,000$ at $8 \%$ simple interest and the remaining at $\frac{4}{3} \%$ simple interest. His total income after a year was ₹ $800$. Find the sum (in ₹) lent at $8 \%$ interest.

What will be the ratio of simple interest earned by a certain amount at the same rate of interest for $6$ years and that of $9$ years?

Deepak lent ₹ $8800$ to Jaichand for $13$ $years$ and ₹ $5500$ to another person for $12$ $years$ at the same rate of simple interest. He received ₹ $14432$ in total as interest from both. The rate of interest (in $\%$) per annum is:

$A$ man took a loan from a bank at the rate of $12 \%$ $p.a.$ simple interest. After $3$ $years$ he had to pay ₹ $5400$ interest only for the period. The principal amount (in ₹) borrowed by him was:

In what time (in $years$) will ₹ $1200$ become ₹ $1344$ at $6 \%$ per annum simple interest?