4-3= 1
So,
1, 10 kg of oil is filled in a 4 kg bottle.
2, 4 kilograms of oil filled with 3 kilograms of bottles.
3, 3 kg becomes 10 kg.
4. Pour the remaining 1kg from the 4kg bottle into the 3kg bottle.
5./kloc-9 of 0/0 kg is filled with 4 kg bottles, and then the remaining half (5 kg).