The compound interest on ₹ $4000$ for $4$ years at $10 \%$ per annum will be (in ₹):

The difference between the compound interest and the simple interest on ₹ $8000$ for $3$ years at $5 \%$ per annum is (in ₹):

The population of a state increases by $10 \%$ every year. If its population in the year $2003$ was $15$ lakhs,what was its population in the year $2005$ (in lakhs)?

Which of the statements given below are sufficient to answer the following question?
What is the rate of interest $p.c.p.a.$ on the amount of $Rs. 15000$ taken as a loan?
$(I)$ The difference between $C.I.$ and $S.I.$ for $2$ years is $Rs. 170$.
$(II)$ The $S.I.$ for $2$ years is $Rs. 2500$.

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