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Primary school mathematics balance test
Math problem in the fifth grade of primary school: weighing with a balance

There are three metal balls, arranged by mass. A ball is the heaviest, followed by B ball, C ball is the lightest, and there is a D ball. Please weigh it twice with the balance to determine the weight ranking of D ball.

This is very simple, because knowing three balls, you only need to compare D with the intermediate quality B ball:

1. If D is heavier than B, compare it with A.. If D is heavier than a ball, its ranking is 1, that is, D>A & gtB& gt;; c; If it is lighter than the ball, it ranks second, that is, A>D & gtB& gt;; C

2. If D is lighter than B ball, compare it with C ball. If the D ball is heavier than the C ball, it ranks third, that is, A>B >; D & gtc; If it is lighter than the C ball, it ranks fourth, that is, A & gtB& gt;; C & gtD