Adealer bought an article for $7 sold it for $8 bought it back for $9 and then sold it for $10 how much profit did he make

To the total amount of money that a dealer spent is $7 + $9 or %16. His revenue from selling the same articles is $8 + $10 which is equal to $18. The profit is the difference between the total revenue and total cost. 
                              profit = $18 - $16 = $2
Thus, the dealer has a profit of $2. 

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