Bindu lends $Rs. 10000$ in four parts to her friends. If she gets $8 \%$ on $Rs. 2000$,$7.5 \%$ on $Rs. 4000$ and $8.5 \%$ on $Rs. 1400$,what percent must she get for the remainder,if the average interest is $8.13 \%$?

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 $Rs.$)?

$A$ lent ₹ $6000$ to $B$ for $2$ $years$ and ₹ $1500$ to $C$ for $4$ $years$ and received altogether from both ₹ $900$ as simple interest. The rate of interest is (in $\%$):

$A$ certain sum is invested for a certain time. It amounts to ₹ $450$ at $7 \%$ per annum. But when invested at $5 \%$ per annum,it amounts to ₹ $350$. Find the sum (in ₹).

Prabhat took a certain amount as a loan from a bank at the rate of $8 \%$ simple interest per annum and gave the same amount to Ashish as a loan at the rate of $12 \%$ per annum on simple interest. If at the end of $12$ years,he made a profit of $Rs. 320$ in the deal,what was the original amount (in $Rs.$)?

What is the $S.I.$ on $Rs. 800$ at $5 \%$ per annum for $3$ years?