SOLUTION: Three circles of diameter 10 cm each touch each other and are bounded together by a rubber band. What is the length of the rubber band if it is stretched completely?

Obviously, their centers (in the section) form equilateral triangle with the side length of 10 cm.


So, add 10 + 10 + 10 = 30 centimeters for linear elements first. 

Then add to it three times the length of the arc of the circle of the radius 5 cm and the central angle of 120 degrees.


So, the final answer is   =  centimeters.