1, the area of the circle is proportional to the radius of the circle. (error)

2. The area of a circle is proportional to the square of its radius. (right)

The area of a circle is proportional to the square of the circumference. (right)

The area of a square is proportional to the length of its sides. (error)

The circumference of a square is in direct proportion to the length of its side. (right)

6. When the area of a rectangle is constant, the length and width are inversely proportional. (right)

7. When the perimeter of a rectangle is constant, the length and width are inversely proportional. (error)

8. When the area of a triangle is constant, the base is inversely proportional to the height. (right)

9. When the trapezoidal area is constant, the sum of the upper and lower bottoms is inversely proportional to the height. (right)

10, the circumference of a circle is directly proportional to the radius of the circle. (error)

1 1. (right)

12. The length of a rectangle is certain, and its width is proportional to its area. (right)

13. The total amount of rice is certain, and the food is inversely proportional to the leftovers. (error)

14. The radius of a circle is proportional to its length. (error)

15. The numerator of the fraction is certain, and the value of the fraction is inversely proportional to the denominator. (right)

16. The floor space is fixed, and the side length of the square brick is inversely proportional to the number of blocks required. ()

17. The floor area is fixed, and the square brick area is inversely proportional to the number of blocks required. ()

18. The divisor is fixed, and the dividend is directly proportional to the quotient. ()

(2) choose.

1. Put a pile of fertilizer into sacks, the number of sacks and the weight of each bag of fertilizer. ()

A. directly proportional; Inverse ratio; be disproportionate

2. Sum some, addend and another addend. ()

A. directly proportional; Inverse ratio; be disproportionate

3. Among the three quantities, the tonnage of each freight, the number of freight pieces and the total tonnage of freight, () is in direct proportion, and () is in inverse proportion.

A the tonnage of a car is fixed at one time, and the quantity and total tonnage of the shipment are fixed.

B the number of cars shipped is fixed, the tonnage of each shipment and the total tonnage of each shipment.

C. The total tonnage of automobile freight is fixed, the tonnage of each freight and the quantity of freight.