I need help in solving the following problem. Three numbers are given: 6, 7, and 8. I need to calculate number of all possible combinations of 9-digit number consisting of 6,7 and 8 which satisfy the following condition: Quantity of 6- four, of 7-three, and of 8-two. So, I need calculate combinations such as 666677788, 687766678, 787678666, etc.
What I did: For a start. I seem to calculate the combinations with four 6s and the remaining combinations of 7 and 8, although I am not 100% sure:
9C4*(2^5). This should give the numbers with four 6s, with quantity of 7s and 8s from 1 to 5. From here, I do not know how to exclude those combinations that do not satisfy the given condition.
What I did: For a start. I seem to calculate the combinations with four 6s and the remaining combinations of 7 and 8, although I am not 100% sure:
9C4*(2^5). This should give the numbers with four 6s, with quantity of 7s and 8s from 1 to 5. From here, I do not know how to exclude those combinations that do not satisfy the given condition.
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