31 floors left 24 25 26 27 28 29 30 How to choose the 5th floor?

The 7 floors can be sorted in two ways:

1.Sort by floor from highest to lowest.

2.Sort by floor from lowest to highest.

Here are the steps to sort from highest to lowest:

1.Remove the selected floors: 24, 25, 26, 27, 28, 29, 30

2.Find the largest floor in the remaining floors: 5

3.Add the largest floor to the selected floor: 5

4.Repeat steps 2 and 3 until all floors are selected.

In order of highest to lowest, the best options for these 7 floors are: 24, 25, 26, 27, 28, 29, 5

Here are the steps to sort from lowest to highest:

1.Remove the selected floors: 24, 25, 26, 27, 28, 29, 30

2.Find the smallest floor of the remaining floors: 5

3.Add the smallest floor to the selected floor: 5

4.Repeat steps 2 and 3 until all floors are selected.

In order from lowest to highest, the best choices for these 7 floors are: 5, 24, 25, 26, 27, 28, 29

26 or 27, I chose the 27th floor, because the air is also good, and this floor is OK, but if the elderly are recommended to have a lower floor, because in case the elevator is out of power, such a high floor is not convenient.

The law is that the first and eighth add up to 55, followed by the second and seventh....So it's 4*55

Choose any four numbers to make up the ratio, which is a:b=c:d.

Alternatively, we can write ad=bc

Among the ten numbers from 21 to 31, if you meet the requirements, it can be 21 = 3 * 7

I didn't find a match for it.

Solution: 21, 24, 27, 30

These four numbers are 7 times, 8 times, 9 times, and 10 times of 3, which is just the proportion, and if you don't understand the wrong meaning, it should be like this.

For this kind of problem, there is a fixed solution, which can be solved in three steps, taking this problem as an example.

<> this way, the sum of horizontal, vertical, and oblique is 81

The law is that the first and eighth add up to 55, followed by the second and seventh....So it's 4*55