有四个数，用其中3个数的平均数，再加上另外的一个数，按这样的方法计算，分别得到：28、36、42、46，那么原来四个数的平均数是多少？

数学题解答：假设28是甲乙丙的平均数+丁，36是甲丙丁的平均数+乙，42是甲乙丁的平均数+丙，46是乙丙丁的平均数+甲，将这四个数加起来，所得的和中包含了两次甲乙丙丁的和，所以这四个数的平均数可以这样算：

28+36+42+46＝152

152÷2＝76…………四个数的和

76÷4＝19…………四个数的平均数

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