A barrel of oil, the first time to use two fifths, the second time to use 10 kg, then the remaining oil just accounts for half of the whole barrel of oil How much oil is there in this barrel

A barrel of oil, the first time to use two fifths, the second time to use 10 kg, then the remaining oil just accounts for half of the whole barrel of oil How much oil is there in this barrel

Let's suppose that the barrel of oil used to be x kg
　　(1-2/5)x-10=(1/2)x
(1/10)x=10
x=100
The barrel of oil used to be 100 kg

A barrel of oil is used up in two times. Two fifths of the oil is used in the first time and two fifths of the kilogram is used in the second time. How many kilogram is there in this barrel of oil?

2/5/(1-2/5)=2/3
This barrel of oil is two thirds of a kilogram