Answer:
The 27th term is 73.5.
Step-by-step explanation:
We want to find the 27th term of the arithmetic sequence:
15, 17.25, 19.5, 21.75, ...
We can write a direct formula. Recall that the direct formula for an arithmetic sequence is given by:
![x_n=a+d(n-1)](https://tex.z-dn.net/?f=x_n%3Da%2Bd%28n-1%29)
Where <em>a</em> is the initial term and <em>d</em> is the common difference.
From the sequence, we can see that our initial term <em>a</em> is 15.
To find the common difference, subtract a term and its previous term. Thus, the common difference will be:
![d=17.25 - 15 = 2.25](https://tex.z-dn.net/?f=d%3D17.25%20-%2015%20%3D%202.25)
Thus, our direct formula is:
![x_n=15+2.25(n-1)](https://tex.z-dn.net/?f=x_n%3D15%2B2.25%28n-1%29)
To find the 27th term, let <em>n</em> = 27. Substitute and evaluate:
![\displaystyle \begin{aligned} x_{27} &=15+2.25((27)-1) \\ &= 15+2.25(26) \\&= 15+58.5 \\ &= 73.5\end{aligned}](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cbegin%7Baligned%7D%20x_%7B27%7D%20%26%3D15%2B2.25%28%2827%29-1%29%20%5C%5C%20%26%3D%2015%2B2.25%2826%29%20%5C%5C%26%3D%2015%2B58.5%20%5C%5C%20%26%3D%2073.5%5Cend%7Baligned%7D)
Thus, the 27th term is 73.5.