Use the number 012345 to form a number without repeating numbers, and find the sum of three digits of all components

Use the number 012345 to form a number without repeating numbers, and find the sum of three digits of all components

There are three digits in three digits, the first digit can't be 0, so there are five choices from 1 to 5. The second digit can choose all the digits except the first digit, so there are five choices from 6-1 = 5. The third digit can choose all the digits except the first and second digit, so there are four choices from 6-1-1. Therefore, there are a total of 5 * 5 * 4 = 100 digits

For example, write out the largest number composed of three identical natural numbers a without operation symbol

The maximum number of different natural number a is not the same
If 1, 111 is the largest
As big as 0
If 2, 2 ^ (22) is the largest
If 3, 3 ^ (33) is the largest
If 4, then 4 ^ (4 ^ 4) = 4 ^ 256
When a ≥ 4, a ^ (a ^ a) is the largest

Use eight numbers 1, 1, 2, 2, 3, 3, 4, 4 to form different four digit numbers. The number is ()
A. 168B. 180C. 204D. 456

① If the four selected numbers are 1, 2, 3, 4, then a44 different four digit numbers can be formed; ② from any two of the four groups (1, 1), (2, 2), (3, 3), (4, 4), C24 can be selected, and each of them can form six different four digit numbers: if 1, 1, 2, 2 are taken, the following six four digit numbers can be obtained: 112222111212212112112 At this time, a total of four different digits of 6c24 can be obtained: ③ from any one of the four groups (1,1), (2,2), (3,3), (4,4), there is C14 method, and then from any two different digits of the remaining three groups, there are C23 methods. Arranging these two different digits into four digits has A24 method, while the remaining two same digits only have A24 method A method, according to the multiplication principle, can be obtained: C14 · C23 · a24 · C22. To sum up, we can use eight numbers 1, 1, 2, 2, 3, 3, 4, 4 to form different four digit numbers, the number is a44 + 6c24 + C14 · C23 · A24 · C22 = 204