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(2) 3、5、4、9

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(2) 14

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(4) 15

(5)30

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(7) 12

(8) 15

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Four fifths and one fifth.

Extended materials use the physical objects around them to demonstrate the conditions and problems of mathematical problems, and the relationship between conditions and conditions, and on this basis, analyze and think, and seek solutions to problems.

Image thinking method, the main means of image thinking are objects, graphics, tables and typical image materials. Its cognitive feature is that it is average in individual performance and always retains its intuition about things.

Its thinking process is represented by representation, analogy, association and imagination. Its thinking quality is manifested in the active imagination of intuitive materials, the processing and refining of appearances, and then the essence, law or object are revealed. Its thinking goal is to solve practical problems and improve thinking ability in solving problems.