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

If a commission at the rate of $10 \%$ is given to a bookseller on the marked price of a book by the publisher, the publisher gains $20 \%$. If the commission is increased to $15 \%$ then the gain percent would be

The price of $12$ chair and $8$ table is Rs. $676 .$ What is the price of $21$ chair and $14$ table in $Rs.$?

Sasha goes to a shop to buy a sofa set and a center table. Ske bargins for a $10 \%$ discount on the center table and and $25 \%$ discount on sofa set. However, the manager, by mistake, interchanged the discount percentage figures while making the bill and Sasha paid accordingly. When compared to what she should pay for her purchases, what percentage did Sasha pay extra given that the center table costs $40 \%$ as much as the sofa set.

Ram sells an article to Girish at a gain $20 \%$, Girish sells it to Sanjay at a gain of $10 \%$ and Sanjay sells it to Aditya at a gain of $12 \frac{1}{2} \% .$ If aditya pay $Rs.\, 59.40.$ What did it cost Ram in $Rs.$?

A man buys an article for $Rs.\;27.50$ and sells it for $Rs.\, 28.60.$ Find the gain percent?