If the interest on ₹ $12000$ is more than the interest on ₹ $10000$ by ₹ $500$ in $3$ $years$,the rate percent 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 $8.13 \%$?

How many years will it take for an amount of $Rs. 600$ to yield $Rs. 120$ as interest at $10 \%$ per annum of $S.I.$?

Mr. Gupta deposits ₹ $3000$ in a bank at $10 \%$ $p.a.$ and ₹ $5000$ in another bank at $8 \%$ $p.a.$. The rate of interest (in $\%$) for the whole sum is

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

$A$ person receives a simple interest of ₹ $1,000$ on a certain principal at the rate of $5 \%$ $p.a.$ in $4$ years. What compound interest (in ₹) will that person receive on twice the principal in $2$ years at the same rate?