$A$ dishonest dealer professes to sell his goods at cost price but uses a weight of $960 \, g$ instead of a $1 \, kg$ weight. Find his gain $\%$. (in $\%$)

Oil equal to $20 \%$ of the weight of groundnut is extracted in a mill. The matter left after extraction is sold as cattle feed at the rate of $Rs. 12.5$ per $kg$. The groundnuts are bought at $Rs. 20$ per $kg$ and the processing cost is $Rs. 5$ per $kg$. At what price ($Rs.$ per $kg$) should the oil be sold to earn $20 \%$ profit on total costs (Total cost $=$ cost of groundnuts and processing costs)?

$A$ tradesman marks his goods $30 \%$ more than the cost price. If he allows a discount of $6 \frac{1}{4} \%$ then his gain percent is

Two items $A$ and $B$ are sold at a profit of $10 \%$ and $15 \%,$ respectively. If the amount of profit received is the same,then the cost price of $A$ and $B$ may be (in $Rs.$)

The cost price of $40$ articles is the same as the selling price of $25$ articles. Find the gain percent. (in $\%$)

$20 \%$ loss on selling price is what per cent loss on the cost price? (in $\%$)