If a sum of money doubles itself in $8$ years at $S.I.$,then the rate of interest per annum (in $\%$) is: (in $.5$)

$A$ man took a loan from a bank at the rate of $12 \%$ $p.a.$ simple interest. After $3$ $years$ he had to pay ₹ $5400$ interest only for the period. The principal amount (in ₹) borrowed by him was:

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 $8.13 \%$?

What annual payment (in $Rs.$) will discharge a debt of $Rs. 1092$ due in $2 \,yr$ at $12 \%$ simple interest?

Two equal amounts are deposited in two banks,each at $15 \%$ per annum,for $3 \frac{1}{2}$ years and $5$ years respectively. If the difference between their interests is ₹ $1440$,each sum is (In ₹):

$A$ person invested $\frac{2}{3}$ of his capital at $3 \%$,$\frac{1}{6}$ at $6 \%$,and the remainder at $12 \%$. If his annual income is $₹ 25$,then the total capital (in $₹$) is: