Find $SP$ when $CP = Rs. 80.40$ and $\text{loss} = 5\%$.

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

$A$ shopkeeper expects a gain of $22 \frac{1}{2} \%$ on his cost price. If in a week,his sale was of $Rs. \,392$,what was his profit? (in $Rs$)

$A$ shopkeeper cheats to the extent of $10 \%$ while buying as well as selling by using false weights. His total gain percentage is:

$A$ fruit-seller buys some oranges and by selling $40 \%$ of them he realizes the cost price of all the oranges. As the oranges begin to grow over-ripe,he reduces the price and sells $80 \%$ of the remaining oranges at half the previous rate of profit. The rest of the oranges being rotten are thrown away. The overall percentage of profit is (in $\%$)

There is a profit of $20 \%$ on the cost price of an article. The per cent of profit, when calculated on the selling price is.......$\%$