Cost of 1 dozen pencils = Rs. 10.80
Cost of 4 dozen pencils = 4 × 10.80 = Rs. 43.2
Selling price of each pencil = 80 paise
Total number of pencils = 12 × 4 = 48
SP of 48 pencils = 48 × 80 paise = 3840 paise = Rs. 38.40
Here, SP < CP.
Loss = CP - SP = Rs. (43.2 - 38.4) = Rs. 4.8
Loss % = (Loss/CP) × 100 = (4.8/43.2) × 100 = 480/43.2 = 11.11%