Final answer:
The number 309 is the 100th term of the arithmetic sequence.
Step-by-step explanation:
To find which term of the arithmetic sequence the number 309 is, we need to use the formula:
Sn = P0 + (n - 1)d
where:
- Sn is the nth term of the sequence
- P0 is the first term
- d is the common difference
Plugging in the given values, we have:
Sn = 12 + (n - 1)3
To solve for n, we set Sn equal to 309:
309 = 12 + (n - 1)3
Simplifying the equation:
297 = 3n - 3
3n = 300
n = 100
Therefore, the number 309 is the 100th term of the arithmetic sequence.