2. If one of A is b=k+4(k must be), A and B are in (positive) proportion; If ab=3k(k must be), A and B become (inverse).

proportion

3. The length of the part measured on the plan with the scale of 6: 1 is 15cm, and the actual length of the part is (25) mm ..

4. The diameter of the small circle and the radius of the big circle are both 4cm, and the simplest integer ratio of the circumference of the big circle and the small circle is (2: 1).

5. In proportion, two extroverts are reciprocal, one is 6 2/3 and the other is (3/20).

6. The survival rate of saplings is certain, and the surviving trees are in (positive) proportion to the total number of saplings.

7. When the chart is enlarged by 2: 1, the length of each side of the chart is enlarged to the original (1/2) times, but the (scale) of the chart remains unchanged.

The second big problem.

1. Draw a ray from the vertex of a right angle and divide the right angle into two angles, so that the ratio of their degrees is 2: 3, and the degree of the larger angle is (b) a.36..

b54

c. 18

d. 108

2. The ratio of 1/3: 1/4 can be (a).

Answer 4:3

b.3:4

C. One quarter: 3

D. One quarter: one third

3. On a map, the actual distance of 30km is represented by a line segment of 20cm, so the scale of this map is (c). a. 1: 1500

1: 15000

c. 1: 150000

d 1: 1500000