The sum of the series below is 10,900. How many numbers, n, are in the series?19 + 20.5 + 22 + 23.5 + ... + 181

This is an arithmetic series with first term 19, last term 181, and common difference 1.5. The sum of an arithmetic series is n times the average of its first and last terms: 10,900 = n × (19 + 181)/2 = 100n. Dividing by 100 gives n = 109, so the correct choice is 109.

AI-written and checked against the verified answer.