Question

An auditorium has 80 rows of seats and the number of seats per row increases at a constant rate. If there are 32 seats in the 8th row, and 68 seats in the 20th row, how many seats are in the last row?

Answer 1

To find how many seats in the 80th row, you need to figure out the pattern from the 8th row to the 20th row.

To do this, you can create a table showing possibilities from the 8th to the 20th.

I started with 32 at the 8th and added 2 each time.  This was only 56 by the 20th.

Then I added 3, and this got me to 68 by the 20th row.

Then you can work backwards to find how many seats in the 1st row.  I got 11.

From here you can create an equation that you could use to solve for the 80th row.

11 + 3(r - 1), where r is the number of rows.

Substitute in 80 for r.

11 + 3(80 - 1)
11 + 237
248 seats

There are 248 seats in the 80th row.