#911 · Combinatorics · Counting
Four‑digit numbers
How many different four‑digit numbers can be formed using four of the six distinct digits 3, 4, 7, 5, 8, 1 (no digit repeated)?
H. S. Hall & S. R. Knight, Higher Algebra (1891) · Ch. XI. Permutations and Combinations, Examples XI.a, No. 7 (part 2)
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