$A$ cloth merchant says that due to a slump in the market,he sells cloth at a $10 \%$ loss,but he uses an inaccurate metre scale and actually gains $15 \%$. Find out the actual length of the scale (in $cm$).

$A$ trader sells his table at a profit of $15 \%$ and the chair at a loss of $7 \frac{1}{2} \%,$ but on the whole he gains $Rs. 50.$ If he sells the table at a loss of $7 \frac{1}{2} \%,$ and the chair at a profit of $15 \%,$ then he neither gains nor loses. Find the cost price of the table.

$A$ shopkeeper professes to sell his goods at cost price but uses a weight of $800 \text{ g}$ instead of a $1 \text{ kg}$ weight. His profit percentage is:

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)?

$A$ fruit seller sells mangoes at the rate of $Rs. 9$ per $kg$ and thereby loses $20\%$. At what price per $kg$ should he have sold them to make a profit of $5\%$? (in $Rs.$)

$A$ shopkeeper sells notebooks at the rate of $Rs.\, 45$ each and earns a commission of $4 \%$. He also sells pencil boxes at the rate of $Rs.\, 80$ each and earns a commission of $20 \%$. How much total commission will he earn in two weeks if he sells $10$ notebooks and $6$ pencil boxes a day? (in $Rs.$)