Several problems about proportion in primary school mathematics

Whose ferrule score is better, the product of two internal terms = 1

So the product of two external terms is 1.

Playing ring games, the product of two internal items = the product of two external items.

The two inner terms are reciprocal, so the product of the two outer terms is (1.

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Because in proportion? Please explain the reason. Write two proportions according to 12×2=3×8.

12, Tian Li used 8 of 10 traps: 8 = 3: 8 = 3: 12.

Proportionally, the two internal terms are reciprocal, and Li Hua uses 28 of the 35 traps: 2.