2004 AMC 10B Problem 2
Problem 2 of 25EasierNumber TheoryCombinatorics
How many two-digit positive integers have at least one as a digit?
Answer choices
Show solution
Solution
The numbers through give with a in the tens place.
The numbers give with a in the units place.
Since is counted twice, the total is
Thus, the correct answer is B.
Tagged: digits · inclusion-exclusion