The first question: the answer is yes, because: there are three cups with their mouths up and one cup with its mouth down.
The first flip: flip two cups up and one cup down, and you get two cups up and two cups down.
The second flip: flip two cups up and one cup down, and then you get three cups down and one cup up.
The third turn: after turning the mouths of three cups down, you get the mouths of four cups up.
Question 2: 7 kg minus 5 kg equals 2 kg. So fill the 7 kg bottle with water, and then pour the water in this bottle into the 5 kg bottle, but after filling it, there is still 2 kg of water left in the 7 kg bottle. Repeat this action for 3 times, which is 6 kilograms of water.
The third question: this month has four full weeks, so we get 28 days. Then add a Monday, and it will be 29 days. This Monday must be the Monday at the end of the month, otherwise there will be no five Mondays. The title also tells us that the beginning and end of the month are not Mondays, so the 29 days we just got are one day earlier and one day later on both sides. There are 3 1 day in all, and the first day is Sunday.
Question 4: I don't know the "best method", so this question has no solution for the time being.
Question 5: There are 2 1 people who participate in the science interest group, and 16 people who participate in the sports interest group. There are 7 people who apply for both, so only 2 1-7 people apply for science and only 16-7 people apply for sports. It is concluded that there are 14 people who only apply for science and 9 people who only apply for sports. Plus those who both apply and don't apply, it is 14+9+7+ 15 = 45 people.
Question 6: This question is a bit of a brain teaser: a teacher has 55 students, that's 56 people, so renting five big boats 1 boat is definitely the most cost-effective, hehe.
Assuming that the bus travels x kilometers per hour, the equation is obtained: (40+X) times 3.5=3 15, so 40+X=90 and X=50.