$A$ 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 $\%$)

$A$ dairyman pays $Rs. 6.40$ per litre of milk. He adds water and sells the mixture at $Rs. 8$ per litre,thereby making $37.5\%$ profit. The proportion of water to milk received by the customers is

$A$ loss of $19 \%$ gets converted into a profit of $17 \%$ when the selling price is increased by $Rs. 162$. Find the cost price of the article in $Rs.$

If the cost price of $20$ tables is equal to the selling price of $25$ tables,find the loss percentage. (in $\%$)

$A$ man invests $Rs. 21,000$ in shares of a company. He sells one-third of the total shares at a profit of $10\%$. However,he has to sell the remaining shares at a $5\%$ loss. Find his overall profit or loss percentage.

$A$ product when sold with $10 \%$ rebate on the listed price gave a profit of $Rs$ $70$. What was its cost price? (in $Rs$)