or
or
The cost price of 100 pens = TK. 420 Cost price of 1 pen = TK. (420/100) = TK. 4.2 Selling price of 1 dozen pens = TK. 60 Selling price of 1 pen = TK. (60/12) = TK. 5
Profit per pen = Selling price per pen - Cost price per pen = TK. (5 - 4.2) = TK. 0.8
Let the number of pens bought be x Total profit = TK. 100
Profit per pen × number of pens = Total profit TK. 0.8 × x = TK. 100 x = (TK. 100)/(TK. 0.8) = 125
Therefore, the man bought 125 pens.
