2. Use the direct ratio formula with work efficiency of 40%: 6 =1:x.
0.4x=6
x= 15
3. Supermarket A: 20÷(4+ 1)=4 (block) 20-4= 16 (block)
Supermarket B: 20×80%= 16 (block)
Both supermarkets pay the original price of 16 moon cakes, so the two supermarkets are the same.