$A$ cloth dealer professes to sell cotton at cost price, but uses a meter scale having a length of $80 \, cm$ only and charges for a full meter. Find his gain percent.

$A$ 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:

$A$ man buys $10$ oranges for a rupee and sells $8$ oranges for a rupee. What is the profit percent?

$A$ sells his house worth $Rs. 10\, lakh$ to $B$ at a loss of $10\%$. Later,$B$ sells it back to $A$ at $10\%$ profit. The result of the two transactions is:

Seema sells a pen to Sapna at a profit of $25 \%$. Sapna sells it to Asha at a profit of $10 \%$ and Asha sells it to Kavita at a profit of $5 \%$. If Asha sells it for $Rs.\,231$,find the cost price at which Seema bought the pen? (in $Rs.$)

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