$A$ man purchased $150$ pens at the rate of $Rs. 12$ per pen. He sold $50$ pens at a gain of $10 \%$. The percentage gain at which he must sell the remaining pens so as to gain $15 \%$ on the whole outlay is........$\%$

$A$ rice trader buys $16$ quintals of rice for $Rs. 5632$. $20 \%$ of the rice is lost in transportation. At what rate should he sell the remaining rice to earn a $25 \%$ profit in $Rs.$ per quintal?

In a certain store,the profit is $320 \%$ of the cost. If the cost increases by $25 \%$ but the selling price remains constant,approximately what percentage of the selling price is the profit?

$A$ fruit-seller buys some oranges and by selling $40 \%$ of them he realizes the cost price of all the oranges. As the oranges begin to grow over-ripe,he reduces the price and sells $80 \%$ of the remaining oranges at half the previous rate of profit. The rest of the oranges being rotten are thrown away. The overall percentage of profit is (in $\%$)

If the $CP$ of $50$ items is equal to the $SP$ of $40$ items,then what is the profit or loss $\%$ (in $\%$)?

$A$ sells a bicycle to $B$ at a profit of $20 \%.$ $B$ sells it to $C$ at a profit of $25 \%.$ If $C$ pays $Rs. 225$ for it,the cost price of the bicycle for $A$ is (in $Rs.$)