that is

945/22.5=42

Then multiply by the number of each group.

Finally,

42×3= 126

2. Teeth can be regarded as the circumference of a circle.

So the perimeter ratio is

A: B = 2 1: 49

Because the rotation speed is only perimeter/time, the rotation speed ratio is equal to the perimeter ratio (the same time is unit time), that is, 21:49 = 420: b.

therefore

B is 980.

3. Re-pouring does not affect the overall volume, so

The total amount remains the same.

The height of the new cylinder is

28.26 * 24/(π 6 2) = (Do it yourself)

4. At the same time, it means that the ratio of shadow length to object length remains unchanged (it is considered that the sun at the same time has the same height and the same inclination is a similar triangle), so

2:22.5=t: 1.8

Just find t

5. According to four paragraphs means according to three times, and that seven paragraphs means according to six times. If it takes t for each setup, then

3t=24

t=8

Seven segments will cost

6×t=6*8=48