The weight ratio of two barrels of oil is 7: 3. If 12kg is taken out of the big barrel and poured into the small barrel, the oil in the two barrels is exactly equal. How many kilograms of oil are there in each of the two barrels?
12 divided by (7-3)=3 3 times 2=6 kg.
6 times 7 = 42kg 6 times 3 = 18kg.
Answer: There are two barrels: the big one is 42kg, and the small one is18kg.