The compound interest on ₹ $30000$ at $7 \%$ per annum is ₹ $4347$. The period (in years) is

$A$ sum of money,deposited at some rate $p.c.p.a.$ of compound interest,doubles itself in $4$ years. In how many years will it become $16$ times of itself at the same rate?

What will be the difference between simple and compound interest (in ₹) at $10 \%$ per annum on a sum of ₹ $1000$ after $4$ years?

$A$ sum of money placed at compound interest doubles itself in $5$ years. It will amount to eight times itself at the same rate of interest in (in $years$):

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

Find the compound interest on $Rs. 12500$ at $8 \%$ per annum for $9$ months compounded quarterly (in $Rs.$).