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例1 某中学初三年级有6个班,从中选出两个班代表学校参加某项活动,三(1)班必须参加,另外再从三(2)班至三(6)班选出1个班．三(4)班有学生建议用如下的方法:从装有编号为1,2,3的三个白球的A袋中摸出一个球,再从装有编号为1,2,3的三个红球的B袋中摸出1个球(两袋中球的大小、形状与质量完全一样),模出的两个球上的数字和是几,就选几班, 你认为这种方法公平吗?请说出理由．
Example 1 There are 6 classes in the third grade of a secondary school, from which two classes are selected to represent the school to participate in an activity, three (1) classes must participate, and another is selected from three (2) to three (6) classes. Classes. Three (4) classes of students suggested using the following method: to draw a ball from the A bag containing the three white balls numbered 1, 2 and 3, and then from the three bags numbered 1, 2 and 3 In the red ball B bag, draw a ball (the size, shape and quality of the ball in the two bags are exactly the same). The number of the two balls on the molded ball is a few, and you can choose a few classes. Do you think this method is fair? Please give reasons.