#851 · Combinatorics · Counting

Finding n from permutation condition

If four times the number of permutations of $n$ objects with three specified objects together equals five times the number of permutations of $n - 1$ objects with three specified objects together, find $n$ .

~3 minAnswer checked instantlypermutationsequations

H. S. Hall & S. R. Knight, Higher Algebra (1891) · Ch. XI. Permutations and Combinations, Examples XI.a, No. 5

Stuck? A gentle nudge

Something off?

Workspace

Your answer

Loading the math keyboard…

Type naturally — sqrt, pi, / and ^ become notation. Any equivalent form is accepted. Press Enter to check.