最简分数的定义 ：分子和分母只有公因数1。

不是最简分数：分子和分母除了公因数1，还有其他公共因数。

                                                                                _{11       33          7             8}

1、分子和分母是倍数关系，那它一定不是一个最简分数。如：-----    -----     -----     ----  ......

                                                                                 ^{22       3            49            56} 

                                                                                                                                    2         6           10       76 

2、分子和分母都是 2 的倍数（末尾数字是：2、4、6、8、0  ）的数，那它一定不是一个最简分数。如：-----    -----     -----     ----  ......

                                                                                                                                    4        38           64        18

                                                                                                                      5         25         30       100

3、分子和分母都是 5 的倍数（末尾数字是：5、0  ）的数，那它一定不是一个最简分数。如：-----    -----     -----     ----  ......

                                                                                                                      10        45          40        5

                                                                                                                                3         6         12         603

4、分子和分母都是 3 的倍数（各数位数字之和是3的倍数 ）的数，那它一定不是一个最简分数。如：-----    -----     -----     ----  ......

                                                                                                                                6         18        33         192

                                                                                                                                                            14     18     22

5、分子和分母都是其他数的倍数（ 如是7的倍数，9的倍数，是11的倍数.......）的数，那它一定不是一个最简分数。如：---    ---     ---  ......

                                                                                                                                                            21     81     33