At what rate per cent per annum will a sum of money double in $16$ years (in $.25$)?

$A$ money lender claims to lend money at the rate of $10 \%$ per annum simple interest. However,he takes the interest in advance when he lends a sum for one year. At what interest rate does he lend the money actually?

An amount fetched a total simple interest of ₹ $3200$ at the rate of $6.25 \%$ per year in $4$ years. What is the amount (principal) in ₹?

If the interest on ₹ $800$ is more than the interest on ₹ $400$ by ₹ $40$ in $2$ years,then the rate of interest (in $\%$) per annum is:

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?

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