$A$ sum of money lent out at simple interest amounts to ₹ $720$ after $2$ $years$ and to ₹ $1,020$ after a further period of $5$ $years$. The sum is (In ₹)

$A$ sum of money invested at $S.I.$ accrued to $Rs. 800$ in $3$ years and to $Rs. 840$ in $4$ years. The rate of interest (in $\%$) per annum is:

₹ $8000$ amounts to ₹ $9200$ in $3$ years at simple interest. If the interest rate is increased by $3 \%$,to how much would it amount (in ₹)?

Mr. Mani invested an amount of ₹ $12000$ at a simple interest rate of $10 \%$ $p.a.$ and another amount at a simple interest rate of $20 \%$ $p.a.$. The total interest earned at the end of one year on the total amount invested was $14 \%$ $p.a.$. Find the total amount (in ₹) invested.

Reena took a loan of ₹ $1,200$ with simple interest for as many years as the rate of interest. If she paid ₹ $432$ as interest at the end of the loan period,what was the rate of interest?

$A$ 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: