$A$ dishonest dealer uses a scale of $90 \, cm$ instead of a metre scale and claims to sell at cost price. His profit percentage is:

When a book is sold at its Marked Price,it gives a profit of $40 \%$. What percentage of profit or loss will occur if it is sold at half the Marked Price?

The cash difference between the selling price of an article at a profit of $4 \%$ and $6 \%$ is $Rs. 3$. The ratio of the $2$ selling prices 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 $25 \% ?$

$A$ shopkeeper marks his goods at $25\%$ above his cost price and allows customers a discount of $12 \frac{1}{2}\%$ for cash. Find his $\%$ profit?

$A$ shopkeeper gains the cost of $8$ metres of thread by selling $40$ metres of thread. Find his gain percent.