Counting intersections — AMC & AIME Problems
Practice every real AMC 8, AMC 10, AMC 12, and AIME problem that uses counting intersections — a combinatorics concept — each with a professionally curated solution, many with a video solution too, from LIVE by Po-Shen Loh. Browse all concepts or the full past-contest archive.
All of these problems are used with official legal permission of the Mathematical Association of America (MAA).
AMC 8
AMC 10
2001 AMC 10 Problem 4 · 2002 AMC 10B Problem 18 · 2010 AMC 10A Problem 22 · 2013 AMC 10A Problem 25 · 2019 AMC 10A Problem 10 · 2019 AMC 10A Problem 14 · 2021 AMC 10B Fall Problem 21
More combinatorics concepts
arrangements with restrictionsbasic countingbijectionBurnside’s LemmaCatalan Numbercircular arrangementscombinationscombinatorial gamecomplementary countingcounting integers in a rangecounting pairscounting regionscounting shapes in figuresderangementsdouble countingfencepost countinggenerating functionsgraph theoryinclusion-exclusionlattice pathsmultiplication principlemultiset permutationspartitions and compositionsPascal’s Trianglepermutationspigeonhole principlerecursive countingstars and barssubsetstilingtree diagramVandermonde’s ConvolutionVenn Diagram