MathCastle
Counting & ProbabilitySuperchallengeCounting Strategies: Casework, Complementary & Overcounting

Counting Strategies: Casework, Complementary & Overcounting · Superchallenge problem

The 77 distinct letters of the word PRODUCT are arranged in a row. How many arrangements have NONE of the three patterns “PR”, “OD”, “CT” appearing as consecutive letters (in that order)?