IOQM · Mathematics

Combinatorics

Counting techniques, pigeonhole, recurrences and elementary graph theory.

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  • Q1 · Combinatorics · HARD

    How many ways can we arrange the letters of the word EQUATION so that no two vowels are adjacent?

  • Q2 · Combinatorics · EASY

    In how many ways can 5 identical red balls and 3 identical blue balls be arranged in a row?

  • Q3 · Combinatorics · MEDIUM

    In how many ways can 5 boys and 4 girls be arranged in a row such that no two girls sit together?

  • Q4 · Combinatorics · HARD

    How many 4-digit numbers can be formed using digits 1, 2, 3, 4, 5, 6 (without repetition) such that the number is divisible by 4?

  • Q5 · Combinatorics · MEDIUM

    In how many ways can the letters of the word OLYMPIAD be arranged such that the vowels O, I, A occupy even positions?

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