If the simple interest on a certain sum of money after $6 \frac{1}{4}$ years is $\frac{3}{8}$ of the principal,then the rate of interest (in $\%$) per annum is

$A$ sum of ₹ $1,550$ is lent out in two parts,one at $8 \%$ and another at $6 \%$. If the total annual income is ₹ $106$,find the money lent at each rate.

Mayuri took a loan at a simple interest rate of $6 \, p.c.p.a.$ in the first year,and the rate increased by $1.5 \, p.c.p.a.$ every year. If she paid $Rs. 8190$ as interest at the end of $3 \, years$,what was her loan amount (in $Rs.$)?

If a certain sum of money at simple interest amounts to ₹ $2800$ in $2$ $years$ and ₹ $3250$ in $5$ $years$,then the rate of interest (in $\%$) per annum is:

$A$ certain sum of money amounts to $Rs. 756$ in $2$ $years$ and to $Rs. 873$ in $3.5$ $years$. Find the rate of interest (in $\%$)?

$Rs. 600$ becomes $Rs. 720$ in $4$ $years$ at simple interest. If the rate of interest is increased by $2 \%$,what will be the total amount (in $Rs.$)?