What will be the compound interest (in ₹) on a sum of ₹ $50000$ after $4$ years at the rate of $10 \%$ per annum?

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

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 $\%$)?

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

Find the least number of complete years in which a sum of money put out at $20 \%$ compound interest will be more than double?

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