A barrel of oil weighs 120 kg. After half of the oil is used, the barrel weighs 65 kg. How many kg is the oil? How many kilos is the barrel?

A barrel of oil weighs 120 kg. After half of the oil is used, the barrel weighs 65 kg. How many kg is the oil? How many kilos is the barrel?

(120-65) × 2 = 55 × 2, = 110 (kg); 120-110 = 10 (kg); answer: oil is 110 kg, barrel weight is 10 kg