How many 10-digit positive integers have all digits either 1 or 2, and have two consecutive 1's?
Question:
How many 10-digit positive integers have all digits either 1 or 2, and have two consecutive 1's?
Answer:
Let's think step by step.

user
880
How many 10-digit positive integers have all digits either 1 or 2, and have two consecutive 1's?
train