$A$ sum of money doubles in $3$ years at compound interest,compounded annually. It will become $4$ times of itself in: (in $years$)

$A$ sum of ₹ $1260$ is borrowed from a money lender at $10 \%$ p.a. compounded annually. If the amount is to be paid back in two equal annual instalments,find out the annual instalment (in ₹).

An amount of money at compound interest grows up to $Rs. 3840$ in $4$ $years$ and up to $Rs. 3936$ in $5$ $years$. Find the rate of interest (in $\%$)?

What would be the $C.I.$ on $Rs. 17500$ at the rate of $12$ $p.c.p.a.$ after $2$ years (in $Rs.$)?

The least number of completed years in which a sum of money put out at $20 \%$ $C.I.$ will be more than doubled is

$A$ certain sum will amount to ₹ $12,100$ in $2$ years at $10 \%$ per annum of compound interest,interest being compounded annually. The sum is (In ₹)