Present age of Bob is equal to Abby's age $8\, years$ ago. Four years hence, the respective ratio between Bob's age and Abby's age will be $4: 5$ at that time. What is Bob's present age? (in $years$)

A man sells two articles, each for $Rs.\,640.$ He earns $20 \%$ profit on the first, and $40 \%$ profit on the second. Find his overall percent profit.

A garment company declared $15 \%$ discount for wholesale buyers. Mr. Ashish bought garments from the company for $Rs.\, 25000$ after getting discount. He fixed up the selling price of garments in such a way that he earned a profit of $8 \%$ on original company price. What is the approximate total selling price? (in $Rs.$)

Half of $100$ articles were sold at a profit of $20 \%$ and the rest at a profit of $40 \% .$ If all of the articles had been sold at a profit of $25 \%,$ the total profit would have been $Rs.\,100$ less than earlier profit. The cost price of each article was (in $Rs.$)

A trader buys two articles for $Rs.\, 4000$ each. While selling if he gains $12.5 \%$ on one and loses $20 \%$ on the other, then what will be the overall loss percent?

A shopkeeper earns a profit of $12 \%$ on selling a book at $10 \%$ discount on the printed price. The ratio of the cost price and the printed price of the book is