There are two formulas: one is how much money three people paid (65438+ 0.8× 3 per person) = how much money the old man received (5 in the old man's hand+0.4 in the old man's hand to buy soda for his grandson), and the other is the six dollars that appeared = the current money in the hands of three people (0.2× 3 per person)+the money in the old man's hand (5)+ the money in the hand of the soda seller.

See, there is nothing wrong with these two formulas, they are both right, but the algorithm given in the question is a typical mixture of two, which is of course inaccurate. If you want to calculate where the 6 yuan money is, press Formula 2, and if you want to calculate how much you paid, use Formula 1. You can't mix them together.

Let me talk about the second question:

The second is not a problem at all. 1 is already equal to 0.9999 ..................................................................................................................................................

For example 1 = 5? =6? But you can't say 5 = 6 is the same. You can't just look at different forms of numbers. The key is to express the same meaning.

1=0.99....=2/2=3/3=5? =6?