If the difference between $S.I.$ and $C.I.$ is $Rs. 25$ on $10000$ for $2$ years,then what is the rate of interest (in $\%$)?

The compound interest (in ₹) on ₹ $800$ for $2 \frac{1}{2}$ years at $5 \%$ per annum is:

$A$ 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 ₹).

Find the difference between $C.I.$ and $S.I.$ on $Rs. 15000$ at $3 \%$ per annum for $3$ years.

$A$ bank offers $5 \%$ compound interest calculated on a half-yearly basis. $A$ customer deposits $Rs. 1600$ each on $1^{st}$ January and $1^{st}$ July of a year. At the end of the year,the amount (in $Rs.$) he would have gained by way of interest is:

$A$ certain sum of money invested at compound interest becomes $1.44$ times of itself in $2$ years. If twice this sum were lent at simple interest, in how many years would it double itself?