To complete this series, we need to identify the pattern or rule that governs the sequence. Let's look at the differences between consecutive terms:
6 - 4 = 2
9 - 6 = 3
13 - 9 = 4
18 - 13 = 5
The differences between consecutive terms are increasing by 1 each time. This suggests that the pattern is that each term is obtained by adding the next number in the sequence to the previous term's difference.
Let's apply this pattern to the last term, 18:
18 + (difference between 18 and the previous term) = 18 + (5) = 23
Therefore, the missing number in the series is 23.
Let's go through each option to determine the correct answer:
Option A) 23 - This option is correct because it follows the pattern we identified.
Option B) 28 - This option is incorrect because it does not follow the pattern.
Option C) 24 - This option is incorrect because it does not follow the pattern.
Option D) 26 - This option is incorrect because it does not follow the pattern.
The correct answer is Option A) 23.