What’s on the Inclusion-Exclusion poster
The rule, 3 worked examples, and the mistake everyone makes.
- Add the sizes, subtract every pairwise overlap, add back every triple overlap, and ke…
- |A ∪ B| = |A| + |B| − |A ∩ B|
- |A|=10, |B|=8, |A∩B|=3 = |A ∪ B| = 15
- Three sets = Σ|A| − Σ|A∩B| + |A∩B∩C|
- Multiples of 2 or 3 to 30 = 15 + 10 − 5 = 20
- Common mistake: Adding |A| + |B| for overlapping sets → Subtracting the intersection…
Derangements fall straight out of this: the number of permutations fixing nothing is n! times the alternating sum of 1/k!.
Questions about the Inclusion-Exclusion poster
- What’s on the Inclusion-Exclusion poster?
- The rule, 3 worked examples, and the mistake everyone makes. Add the sizes, subtract every pairwise overlap, add back every triple overlap, and ke…; |A ∪ B| = |A| + |B| − |A ∩ B|; |A|=10, |B|=8, |A∩B|=3 = |A ∪ B| = 15; Three sets = Σ|A| − Σ|A∩B| + |A∩B∩C|; Multiples of 2 or 3 to 30 = 15 + 10 − 5 = 20; Common mistake: Adding |A| + |B| for overlapping sets → Subtracting the intersection…. Derangements fall straight out of this: the number of permutations fixing nothing is n! times the alternating sum of 1/k!.
- Who is the Inclusion-Exclusion poster for?
- Inclusion-Exclusion belongs to the Mathematics section rather than to a school year, because math is not something one grade owns. Anyone learning discrete mathematics can pin it up — a beginner, a student mid-course, or someone revising years later.
- When should you use the Inclusion-Exclusion poster?
- Any count of items satisfying at least one of several overlapping conditions. A wall chart earns its place by being glanceable from where the work is happening, so Inclusion-Exclusion belongs on the wall where that math work actually happens, within glancing distance, rather than filed away.
- What other posters go with Inclusion-Exclusion?
- The Binomial Theorem, Counting Principles and Euler & Hamiltonian Paths sit alongside Inclusion-Exclusion in the Mathematics section. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.The Binomial TheoremCounting PrinciplesEuler & Hamiltonian Paths
- Is the Inclusion-Exclusion poster free to download and print?
- Yes. Inclusion-Exclusion downloads as a free PDF with no account, no email and no watermark, like everything else in the Mathematics section. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
- What size does the Inclusion-Exclusion poster print at?
- Inclusion-Exclusion is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of Inclusion-Exclusion loses nothing.Printing guide
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