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Additional questions in the first grade math exam.
Let the AB velocity of the small robot be X Y m/min and the radius be r.

8 times 2pie r> = (x+y) *15 > =7 times 2πr

10 times 2pie r> = (x+y+6) *15 > =9 times 2πr

You can get it by adding 90 at the same time.

8 times 2pie r+90 > =(X+Y+6)* 15 & gt; =7 times 2 Pie R+90

Meet the following formula, then

8 times 2pie r+90 > =9 times 2 pie r and 10 times 2 pie R & gt=7 times 2 pie R+90.

The result is 9.5.

Therefore, the minimum diameter is10m, and the maximum diameter is 28m.