MathCastle
Counting & ProbabilityHardCounting Strategies: Casework, Complementary & Overcounting

Counting Strategies: Casework, Complementary & Overcounting · Hard problem

A 55-character code is formed from the digits 00-99, with repetition allowed. How many codes contain at least 22 even digits (the digits 0,2,4,6,80,2,4,6,8)?