The difference between the $S.I.$ and $C.I.$ obtained on a principal amount at $5$ $p.c.p.a.$ after $2$ years is $Rs. 35$. What is the principal amount (in $Rs.$)?

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 $\%$)?

In a certain number of years,a sum of money doubles itself at $6 \frac{1}{4} \%$ simple interest per annum. The required time (in $years$) is:

$A$ sum of money lent at compound interest for $2 \, yr$ at $20 \% \, p.a.$ would fetch $Rs. 964$ more,if the interest was payable half-yearly than if it was payable annually. What is the sum (in $Rs.$)?

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 $Rs. 2500$.

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