1, five classes are scored on average, and each class is assigned one fifth of the total, that is,1/5; Each shift is allocated 3 * 20/5 = 12kg.

12/20=0.6 cases or 3/5 cases.

2. Each piece of wood is one of 9 pieces, namely1/9; Each section is 8/9 meters long; The average sawing time is one of 9 times: 1/9.

3. On average, one kilogram of peanuts can be squeezed: 2/3 kilograms of oil, and it takes 3/2= 1.5 kilograms of peanuts to squeeze one kilogram of oil.