The problem of the fourth grade math problem square: there are 180 students in the fourth grade, arranged in a three-layer hollow square. How many people are there on each side of the outermost layer of this square? Solution: Let's say that there are X people on each side of the outermost layer of this square.

As can be seen from the picture, there are always two people on each side of the inner floor than the outer floor.

The formula for calculating the number of people on each floor is: (number of people on each side-1)×4.

The equation can be obtained: 4× (x-1)+4× (x-3)+4× (x-5) =180.

Solution: x= 18

A: There are 18 people on both sides of the outermost layer.