Simple interest received by a person in $10$ $years$ on a principal of ₹ $9500$ is $130 \%$ of the principal. What is the rate of interest (in $\%$) per annum?

Anil invested an amount for $3$ $years$ at a simple interest rate of $9$ $p.c.p.a.$ He got an amount of $Rs. 19050$ at the end of $3$ $years.$ What principal amount (in $Rs.$) did he invest?

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 $Rs.$)?

$A$ sum of money becomes $\frac{8}{5}$ of itself in $5$ $years$ at a certain rate of interest. The rate per cent per annum is

$A$ sum of money doubles itself in $8$ years. In how many years will it treble?

$A$ sum fetched a total simple interest of $Rs. 4016.25$ at the rate of $9 \%$ $p.a.$ in $5$ years. What is the sum (in $Rs.$)?