Of all the four-digit positive integers containing only digits from the set {2,4,6,8} what fraction of them have at least one 8?
Are you sure you got the question right?
You want 4-digit integers and your set also has 4 digits, therefore all 4-digit permutations will have one 8 in them as follows:
{{2, 4, 6, 8}, {2, 4, 8, 6}, {2, 6, 4, 8}, {2, 6, 8, 4}, {2, 8, 4, 6}, {2, 8, 6, 4}, {4, 2, 6, 8}, {4, 2, 8, 6}, {4, 6, 2, 8}, {4, 6, 8, 2}, {4, 8, 2, 6}, {4, 8, 6, 2}, {6, 2, 4, 8}, {6, 2, 8, 4}, {6, 4, 2, 8}, {6, 4, 8, 2}, {6, 8, 2, 4}, {6, 8, 4, 2}, {8, 2, 4, 6}, {8, 2, 6, 4}, {8, 4, 2, 6}, {8, 4, 6, 2}, {8, 6, 2, 4}, {8, 6, 4, 2}}==24 permutations.
Note: Check your question carefully. I think there is something missing.
