Subject: mathqa
Question: a trader cheats both his supplier and customer by using faulty weights . when he buys from the supplier , he takes 10 % more than the indicated weight . when he sells to his customer , he gives the customer a weight such that 10 % of that is added to the weight , the weight claimed by the trader is obtained . if he charges the cost price of the weight that he claims , find his profit percentage .
Option: 
A: 22.109 %
B: 21 %
C: 20 %
D: 21.33 %
Answer: B