According to the diagram, we use three circles to represent three cans, and the outer ring line can be regarded as a figure tied with plastic ropes. It can be seen that the outer ring figure consists of three straight lines and three arcs. That is, a rope consisting of three A's and three B's.

In the picture, we connect three centers and draw by connecting each center with their two tangents. As can be seen from the figure, according to the tangent principle, a is the sum of the radii of two circles, that is, the length of the diameter of a, 12 cm. B can be obtained by finding the arc length formula, because the central angle is120 (360-60-90-90 =120). At this time, we can also find that it takes three arcs to find the length of a round rope, which is exactly the circumference of a circle. Each is 120, and three are exactly 360.

Then, we can find that the length of a circle of plastic rope = 3a+3b = π d+3 *12 = 3.14 *12+36 = 73.68 cm.

So the length of the last three turns is 3*73.68=22 1.04cm.