#910 · Combinatorics · Counting
Choosing four digits
How many different selections can be made by taking four of the six distinct digits 3, 4, 7, 5, 8, 1?
H. S. Hall & S. R. Knight, Higher Algebra (1891) · Ch. XI. Permutations and Combinations, Examples XI.a, No. 7 (part 1)
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