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

$A$ trader had $1200 \ kg$ of rice. He sold a part of it at $5 \%$ profit and the rest at $11 \%$ profit,so that he made a total profit of $7 \%$. How much (in $kg$) rice did he sell at $5 \%$ profit?

$A$ shopkeeper sold an article at the rate of $Rs. 35$ per article and earned a profit of $40\%$. At what price should each article have been sold to earn a profit of $60\%$?

$A$ man invests $Rs. 21,000$ in shares of a company. He sells one-third of the total shares at a profit of $10\%$. However,he has to sell the remaining shares at a $5\%$ loss. Find his overall profit or loss percentage.

$A$ shopkeeper allows a discount of $10 \%$ on the marked price of a camera. The marked price of the camera,which costs him $₹ 600$,to make a profit of $20 \%$ should be (in $₹$):

Two-thirds of a consignment was sold at a profit of $5 \%$ and the remainder at a loss of $2 \%$. If the total profit was $Rs. 400$,what was the total value of the consignment in $Rs.$?