GAIN 20% on the selling price of 7.20/kgFormula Used:SP = {100/(100 + P%)} × CP,Where,SP is selling price,CP is cost price,P% is profit percent.Calculation:SP of a mixture = 7.20/kgCP of a mixture = 100/120 × 7.20⇒ CP of a mixture = Rs. 6/kgNow by using allegation,Now the ratio = 0.6 : 2⇒ 8/kg : 5.40/kg = 3 : 10According to the question,⇒ 10 = 36kg⇒ 1 = 3.6 kgNow, 3 = 3 × 3.6 = 10.8 kg∴ Total quantity of Rs. 8/kg is 10.8kg.