Question

The River Ridge High School auditorium has exactly 27 rows of seats. The rows are labeled, in order, from the front of the auditorium to the back from A through AA. There are 9 seats in the row A. Each row after the first row has three more seats than the previous row. How many seats are there in row AA?

Answer 1

Answer: 95 seats

Explanation:

I added 3 to each row starting with the 9 seats, up to 27 rows.

Answer 2

87

Explanation:

The numbers of seats in each row form an arithmetic sequence. The general term (an) of such a sequence is given in terms of the initial value (a1) and the common difference (d) as ...

an = a1 + (n-1)·d

The 27th term of the sequence with first value 9 and common difference 3 is ...

a27 = 9 + (27-1)·3 = 9 +78 = 87

There are 87 seats in row AA.