$A$ shopkeeper gains $17 \%$ after allowing a discount of $10 \%$ on the marked price of an article. Find his profit percent if the article is sold at the marked price allowing no discount. (in $\%$)

$A$ shopkeeper loses $7 \%$ by selling a cricket ball for $Rs. 31$. For how much should he sell the ball so as to gain $5 \%$? (in $Rs.$)

If the cost price of $12$ pens is equal to the selling price of $8$ pens,find the gain percent.

$A$ sold a horse to $B$ for $Rs. 4800$ by losing $20\%$. $B$ sells it to $C$ at a price which would have given $A$ a profit of $15\%$. $B$'s gain is (in $Rs.$)

$A$ person sells taperecorders at $Rs. 1134$ each after giving a discount of $19 \%$ on the marked price. Had he not given the discount,he would have earned a profit of $40 \%$ on the cost price. The cost price of each taperecorder is (in $Rs.$)

$A$ 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.