The difference between $C.I.$ and $S.I.$ on $Rs. 700$ in $2$ years at $5 \%$ per annum is (in $Rs.$):

What sum will give ₹ $244$ as the difference between simple interest and compound interest at $10 \%$ per annum in $1 \frac{1}{2}$ years,compounded half-yearly?

$A$ sum of money placed at compound interest doubles itself in $4$ $years$. In how many $years$ will it amount to four times itself?

On what sum will the compound interest (in ₹) for $2 \frac{1}{2}$ years at $10 \%$ per annum amount to ₹ $6352.50$?

$A$ sum of money at compound interest amounts to thrice itself in $3$ years. In how many years will it be $9$ times itself?

An amount of ₹ $8000$ was deposited at simple interest for $3$ years at $7.5$ $\%$ per annum. How much more would have been gained (in ₹) had it been deposited at the same rate per cent compound interest?