New posts in Inclusion Exclusion

Showing an alternating sum is positive

Number of ways to arrange word 'KBCKBCKBC'

Combinatorics meaning of $L_m=\sum_{j=m}^{n}(-1)^{j-m}\binom{j-1}{m-1}S_j$

Probability that a stick randomly broken in three places can form a triangle

Which jigsaw pieces fit to make a create a square?

Find the number of ways so that each boy is adjacent to at most one girl.

What is the cardinality of the union A∪B∪...∪Z?

Use Inclusion-Exclusion to find the number of arrangements of 4 A's, 5 B's, 6 C's, 7 D's , 8 E's with exactly 2 adjacent C's

Number of Derangements of the word BOTTLE

Prove this identity with a combinatorial argument