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

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 man buys an article for $10 \%$ less than its value and sells it for $10 \%$ more than its value. His gain or loss percent is

Anil bought an item with $12 \frac{1}{2} \%$ discount on the labellea price. He sold the item with $17 \frac{1}{2} \%$ profit on the labelled price. What was, his percent profit on the price he bought?

While selling an article for $Rs.\, 18450,$ a person suffered a loss of $50 \%$. At what price he should have sold the article (in $Rs.$) to earn a profit of $50 \% ?$

A shopkeeper buys an article at $8$ for $Rs\,16$ and sells them at $9$ for $Rs\,20$. What is his gain or loss percent?