A grocer sells rice at a profit of 10% and uses weight which are 20% less than the market weight. The total gain earned by him will be?

Let us consider a packet of rice marked 1 kg
Then its actual weight = (80% of 1 kg) = 0.8 kg
Let C.P. of 1 kg be Rs. 100
Then C.P. of 0.8 kg = Rs. 0.8 x 100 = Rs. 80
Now, S.P of 1 kg = 110% of C.P.of 1 kg = Rs. 110
⇒ Gain = (1.1 - 0.8) x 100 = 0.3 x 100 = 130
⇒ Required gain% = [0.3/ (0.8 x 130)] x 100)%
= 37. 5%