The first type is divided into 10, 20, 30.

(1) and 10 in the middle. Because of the reason of folding in half, as long as you cut five strips, 10 will be produced, so the crease is at the position of 25cm or 35cm.

(2), the middle 20, cut 10, crease at the position of 20cm or 40cm.

③ When 30 is in the middle, cut 15, and the crease is at the position of 25cm or 45cm.