Question

The first row of a section in a concert hall has 20 seats. The second row has 21 seats. The third row has 22 seats. This pattern continues and this section has 12 rows. How many seats are in this section?

Answer 1

The correct answer is 306. I took the test.

Answer 2

To solve this problem you must apply the proccedure shown below:

1. The arithmetic sequence is:

`an=a1+d(n-1)`

Where
`an` is the nth termn,
`a1` is the first term,
`d` is the common difference between the terms and
`n` is the number of the term.

2. Based on the information given in the problem, you have:

`a1=20\\ d=1\\ n=12`

3. When you substitute these values into the formula, you obtain:

`an_(12) =20+(12-1)\\ a_(12)=31`

The answer is:
`31` seats