The distance between holes is the distance between holes, right? Otherwise, this one is a little abnormal, with too many decimals. And this depends on how many holes can be drilled at most, because there are two ways, one is concentric arrangement and the other is horizontal and vertical arrangement.

Analysis: Because it is a circle, the radial direction and circumferential direction should be considered when the gap is equal. The following is calculated in CM:

1. The number of concentric circles can be 240/ 10/2= 12.

2. You can drill a hole in the first concentric circle, because it is just at the center of the circle 1.

Concentric circles, pi, diameter spacing and number of holes can be rounded off.

1 0 10 1 1

2 3. 14 20 10 6.28 6

3 3. 14 40 10 12.56 12

4 3. 14 60 10 18.84 18

5 3. 14 80 10 25. 12 25

6 3. 14 100 10 3 1.4 3 1

7 3. 14 120 10 37.68 37

8 3. 14 140 10 43.96 43

9 3. 14 160 10 50.24 50

10 3. 14 180 10 56.52 56

1 1 3. 14 200 10 62.8 62

12 3. 14 240 10 75.36 75

The total number of holes available is 4 16.

Stupid way, I don't know if there is a better way. I've lost my advanced math for too long.