By selling 8 dozen of pencils, a shopkeeper gains the selling price of a 1 dozen pencils. His gain percent is?

∵ Gain = (S.P. of 8 dozen ) - (C.P. of 8 dozen )
⇒ (S.P. of 1 dozen) = (S.P. of 8 dozen ) - (C.P. of 8 dozen)
∴ (C.P. of 8 dozen ) = (S.P. of 7 dozen)
Let C.P. of each dozen be Re. 1
⇒ C.P. of 7 dozen = Rs. 7
⇒ S.P. of 7 dozen = Rs. 8
∴ Gain % = (1 / 7 x 100)% = 14²/₇ %