Give you 30 yuan, let you buy 1 yuan a bottle of mineral water (every 2 empty bottles can change 1 bottle of mineral water) ask you how many bottles of mineral water you can drink at most

Give you 30 yuan, let you buy 1 yuan a bottle of mineral water (every 2 empty bottles can change 1 bottle of mineral water) ask you how many bottles of mineral water you can drink at most

30+30÷2+14÷2+（7+1）÷2+4÷2+2÷2
=30+15+7+4+2+1
=59

One yuan can buy a bottle of soda, two empty bottles can change one, 20 yuan, how many bottles of soda can I drink at most?
Can you give me some analysis process

20 + 10 + 5 + 2 + 1 + 1 = 39 A 40 bottle friend is really talented. I give you a regular way: first buy 20 bottles to drink, 20 empty bottles for 10 bottles, drink 10 bottles, use 10 empty bottles for 5 bottles to drink, use 4 out of 5 empty bottles for 2 bottles to drink, then there are 3 empty bottles left, change one bottle to drink, then there are 2 empty bottles left, and then change one bottle, a total of 39 bottles were drunk

What is the material of mineral water bottle?

There are cool beverage bottles, mineral water bottles, liquid food bottles, cosmetics bottles, etc. the materials used are polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), etc
Usually, mineral water bottles are made of PVC or pet,
Carbonated beverage bottles are made of pet,
Cool drink bottles, liquid food bottles are made of PVC and PE