That is, perimeter = radius X 2 X 3. 14.
In this multiplication, the radius is the multiplier and the circumference is the product. How many times the multiplier (radius) is enlarged, how many times the product (perimeter) is enlarged. So it is proportional.
(2) It is inversely proportional, because the yield per hectare * the number of hectares sown = the total output (certain), so it is directly proportional.
(3) Out of proportion, because the two quantities are irrelevant to each other.
(4) It is inversely proportional, because in any case, the area of each piece of land * the number of blocks needed = the area of the house (certain), so it is inversely proportional.
(5) It is directly proportional, because 1/3 bottom area * height = cone volume, and the cone surface area is certain and inversely proportional.
4.( 1)b (2)c (3)a (4)c (5)b
5. According to the formula, 7/a=b/7 is reduced to ab=49, so it is inversely proportional.
When finished, whether it is right or not, adopt it and give it a good evaluation or something.