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The math class is up to standard. Seventh grade, page 92, the third question.
First of all, considering the particularity of paper-cutting, each crease can form an axis of symmetry.

This topic is to study the change law of crease through the change of folding times. There are creases in the first folding, and there are two layers of paper after the first folding. After the second folding, there is a crease in each of the existing two layers, and the original crease * * * is 1+2 = 3 = 2? -1 crease, the paper * * * has four layers after being folded twice, and four creases are added on the basis of three creases after being folded for the third time, so * * * has 1+2+4 = 7 = 2 cubic meters-1 crease at this time, so it can be seen that * * * is folded for the fourth time.

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