For what sum (in ₹) will the simple interest at $R \%$ per annum for $2$ years be $R$?

The simple interest accrued on a certain principal is ₹ $1200$ in $4$ years at the rate of $8 \%$ per annum. What would be the simple interest (in ₹) accrued on thrice of that principal at the rate of $6 \%$ per annum in $3$ years?

If a sum of ₹ $9$ is lent to be paid back in $10$ equal monthly instalments of ₹ $1$ each,then the rate of interest 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 ₹)?

If ₹ $640$ amounts to ₹ $832$ in $2$ years,what will ₹ $860$ amount to in $4$ years at the same rate of interest per annum (in ₹)?

An investor invested his savings in the stock market. The value of his investments increased by $12 \%$ and $9 \%$ in the first year and the second year respectively. If the value of his investments after two years became ₹ $97,664$,then how much had he invested (in ₹)?