✔ 最佳答案
Case 1: the units digit is 0.
There are 9 x 8 x 7 ways, ie 504.
Case 2: the units digit is 5.
As the thousands digit cannot be 0. So there only 8 x 8 x 7 ways, ie. 448.
So, totally there are (504 + 448) ways, ie. 952 ways. (ans.)
First of all, there are 9 x 9 x 8 x 7 x 6 ways to form a 5-digit number, ie 27216.
Now, try to calc. How many 5-digit number that are divisible by 10.
Same as the previous question, as only 0 can be the units digit,
there are only (9 x 8 x 7 x 6) ways, ie 3024 ways.
So there are only (27216 - 3024) numbers that are not divisible by 10 can be formed, ie. 24192. (ans.)
(as number is formed by the cards, so all digits are different.)