$A$ man buys a watch for ₹ $1950$ in cash and sells it for ₹ $2200$ at a credit of $1$ $year$. If the rate of interest is $10 \%$ $p.a.$,what is his profit or loss?

Two equal sums were lent at simple interest for $4$ years and for $3$ years respectively. The rate of interest in the latter case was $3 \%$ higher than that of the former case,but the amount in each was $Rs. 1088$. Find the rate of interest (in $\%$) of the former case?

Arun gives his wife Asha a birthday gift,giving her each year a number of rupees equal to the number of years of her age. If her birthday falls on $August \, 8$,what sum must be placed at simple interest at $7 \%$ on $January \, 1$,before she is $42$,in order to raise the required sum (in $Rs.$)?

What sum lent at $10 \%$ per year on $S.I.$ will amount to $Rs. 450$ in $2$ years?

$A$ sum of money at simple interest becomes four times in $24$ years. The rate per cent of interest per annum is

Nitin borrowed some money at the rate of $6 \% \text{ p.a.}$ for the first three years,$9 \% \text{ p.a.}$ for the next five years,and $13 \% \text{ p.a.}$ for the period beyond eight years. If the total interest paid by him at the end of eleven years is ₹ $8,160$,the money borrowed by him was: