The weight of a barrel of oil: the weight of B barrel of oil = 1:9 As can be seen from the meaning of the question, the weight difference between the two barrels of oil is 12*2(24) kg. Then, 24/(9- 1) = 3kg, and the weight of barrel oil is 3 *1= 3kg; The weight of barrel B oil is 3 * 9 = 27kg. Verification: 27-12 =12+3 =15, so the result is correct.