There are six kinds. When the digits are 1, 2, 3, there are two ways to select a digit, so there are 2x3x2x 1 = 36, ***48.
Two: In odd numbers, there are three ways to select units: 1, 3, 5. When there is 0, it can only be ten digits, so there is 3×5 = 15, and when there is no 0, it is 3×5×4 = 60. * * * There are 75 kinds. Even numbers, 95 kinds can be obtained by the same method, and the ratio is 15.
Three: space insertion method, the first solo is 5x4x3x2x 1= 120, with six spaces, 6x5x4= 120, * * You120 =/kloc-.