The seller sold a total of 40 kg of rice bags, comprising Basmati Rice and Brown Rice. The cost price of Basmati rice is Rs.72/kg, and that of Brown rice is Rs.84/kg. If the seller sold all the rice bags for Rs.3,816 and earned a profit of 20%, determine the quantity of Basmati rice bags sold.

ATQ, Let, the quantity of Basmati rice bag and Brown rice bag sold be 'a' kg and 'b' kg, respectively. Total cost price of 40 kg Rice bags sold = (3816/1.2) = Rs.3,810 So, the per kg cost price of rice bag sold = (3810/40) = Rs.79.5 ATQ, [(72 × a + 84 × b) /(a + b) ] = 79.5 Or, 72a + 84b = 79.5 × (a + b) Or, 72a + 84b = 79.5a + 79.5b Or, 79.5a - 72a = 84b - 79.5b Or, 7.5a = 4.5b Or, b = (7.5a/4.5) Or, b = (7.5a/4.5) So, b = (5a/3) a + b = 40 Or, a + (5a/3) = 40 Or, 3a + 5a = 40 × 3 Or, 8a = 120 Or, a = (120/8) So, a = 15 So, the quantity of Basmati rice bag sold = a = 15kg