$A$ vendor bought toffees at $6$ for a rupee. How many for a rupee must he sell to gain $20 \%$?

$A$ trader allows a trade discount of $20 \%$ and a cash discount of $6 \frac{1}{4} \%$ on the marked price of the goods and gets a net gain of $20 \%$ of the cost. By how much above the cost should the goods be marked for the sale? (in $\%$)

$A$ shopkeeper gains the cost of $8$ metres of thread by selling $40$ metres of thread. Find his gain percent.

$A$ man purchased $150$ pens at the rate of $Rs. 12$ per pen. He sold $50$ pens at a gain of $10 \%$. The percentage gain at which he must sell the remaining pens so as to gain $15 \%$ on the whole outlay is........$\%$

Albert buys $4$ horses and $9$ cows for $Rs. 13400$. If he sells the horses at $10 \%$ profit and the cows at $20 \%$ profit,then he earns a total profit of $Rs. 1880$. The cost price of a horse is (in $Rs.$)

The marked price of a clock is $Rs. 3200$. It is sold at $Rs. 2448$ after two successive discounts. If the first discount is $10 \%$,then the second discount is.........$\%$