If the interest on ₹ $800$ is more than the interest on ₹ $400$ by ₹ $40$ in $2$ years,then the rate of interest (in $\%$) per annum is:

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 $8.13 \%$?

Ram deposited a certain sum of money in a company at $12 \%$ per annum simple interest for $4$ years and deposited an equal amount in a fixed deposit in a bank for $5$ years at $15 \%$ per annum simple interest. If the difference in the interest from the two sources is $Rs. 1350$,then the sum (in $Rs.$) deposited in each case is:

$A$ sum of ₹ $16800$ is divided into two parts. One part is lent at a simple interest rate of $6 \%$ per annum and the other at $8 \%$ per annum. After $2$ years,the total amount received is ₹ $19000$. The sum lent at the rate of $6 \%$ simple interest (in ₹) 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.

$A$ certain amount earns simple interest of ₹ $1,750$ after $7$ years. Had the interest rate been $2 \%$ more per annum,how much more interest would it have earned (in ₹)?