If the selling price of $\frac{2}{3}$ of a certain quantity of milk be equal to the cost price of whole milk, then what will be the gain percent in this transaction?

By selling 80 ball pens for $Rs.\, 140$ a retailer loses $30 \%$. How many ball pens should he sell for $Rs.\, 104$ so as to make a profit of $30 \% ?$

The cost price of $20$ articles is the same as selling price of $x$ articles. If the profit is $25 \%,$ then the value of $x$ is

At what price should a shopkeeper mark a radio that costs him $Rs.\,1200$ in order that he may offer a discount of $20 \%$ on the marked price and still make a profit of $25 \% ? \quad$ 

Mr. Kapur purchased two toy cycles for $Rs. 750$ each. He sold these cycles, gaining $6 \%$ on one and losing $4 \%$ on the other. The gain or loss percent in the whole transaction is

If the discount of $10 \%$ is given on the marked price of a radio, the gain is $20 \%$. If the discount is increased to $20 \%,$ the gain is......$\%$