The perimeter and side length of a square. (proportional)

The height, area and bottom of a triangle are fixed. ( )

This ratio is fixed and is the ratio of the former to the latter. ( )

The area of the classroom is certain, the number of students in this class and the per capita area. ( )

The height of a cone is fixed, and so is its bottom area and volume. ( )

That's the topic! ! !