To find the sum of the arithmetic sequence 3, 5, 7, 9, 21, we first need to identify whether the numbers provided actually form an arithmetic sequence. An arithmetic sequence is a sequence of numbers in which the difference between consecutive terms is constant.
Examining the given numbers:
- 5 – 3 = 2
- 7 – 5 = 2
- 9 – 7 = 2
- 21 – 9 = 12
The difference between 3 and 5, 5 and 7, and 7 and 9 is 2, but the difference between 9 and 21 is 12. Therefore, these numbers do not form a traditional arithmetic sequence.
However, if we are looking for the sum of these specific numbers regardless of their sequence type, we can simply add them together:
- 3 + 5 = 8
- 8 + 7 = 15
- 15 + 9 = 24
- 24 + 21 = 45
So, the sum of the sequence is 45.