How many three digits can be made up of 123456? How many three digits can be divided by 5 without repetition? twenty

Using tree diagram to solve problems
1 is divided into 1,2,3,4,5,6, and each number is further divided into 1,2,3,4,5,6
2,3,4,5,6, all like this, there are 6 * 6 * 6 = 216
What is divisible by five is five in one place,
When 1 is set, the separated number is qualified as 125135145165 because there is no duplicate number
The same 2, 3, 4 and 6 are also the same in the hundredth, with 4 in each group
Because when 5 is a hundred, there must be repeated numbers when it is rounded out by 5, so there is no consistent number
So there are 4 * 5 = 20

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