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! ! !