I'll attack the last one.
For this one, connect the 3 centers of the holes and you form an equilateral triangle.
Next, draw a radius from the center of the big circle to a vertex.
Now draw a perpendicular to the base of the triangle.
What you have formed now is a 30-60-90 triangle.
You can find the hypotenuse by taking half the diameter of the big circle.
That would be 162.5.
Using your 30-60-90 rules (or trigonometry, if you prefer), you can determine the apothem of the equilateral triangle.
It's half the hypotenuse or 81.25
Finally, the base of the right triangle that you formed can be determined by a number of different ways:
You should find that length to be
Multiply this answer by 2 and you have your desired result.