What will be the net discount (in $\%$) after giving three successive discounts of $10 \%$,$20 \%$,and $30 \%$?

The banker's gain on a certain sum due in $2 \text{ years}$ at $5 \%$ per annum is $Rs. 8$. The present worth is (in $Rs.$)

$A$ dealer purchased an article for $Rs. 900$ and fixes the list price in such a way that he gains $20\%$ after allowing $10\%$ discount. What is the list price (in $Rs.$)?

$Rs. 20$ is the true discount on $Rs. 260$ due after a certain time. What will be the true discount on the same amount due after half of the earlier time,the rate of interest being the same? (in $Rs.$)

The marked price of a laptop is $Rs. 12000$. In a clearance sale,it is sold at a discount of $15\%$,incurring a loss of $4\%$. What is the cost price of the laptop? (in $Rs.$)

If two successive discounts of $20 \%$ and $30 \%$ are given,what is the net discount (in $\%$) ?