Question

The seats at a local baseball stadium are arranged so that each row has five more seats than the row in front of it. If there are four seats in the first row, how many total seats are in the first 24 rows?
@kc_kennylau

Answer 1

\[a_{n}=a_{n-1}+5\]

Answer 2

So the difference is 5.

Answer 3

A1 = 4

Answer 4

Do you know how to find a sum of an arithmetic series?

Answer 5

Where did you get the formula from @SolomonZelman

Answer 6

Which one the first thing I wrote?

Answer 7

Yes that

Answer 8

Well, because each next row is 5 seats more than the previous row.

Answer 9

The 24th row would be \[A_n=a_1+d(n-1)\]in your case, for the 24th row, \[A_{24}=4+5(24-1)\]

Answer 10

207?

Answer 11

No, 119.
After you find the 224th row, use this:
\[S_n=\frac{n(a_1+a_n)}{2}\]

Answer 12

I meant the 24th not 224th.

Answer 13

BUT 9*23=204

Answer 14

@SolomonZelman

Answer 15

why 9 ?

Answer 16

5+4=9

Answer 17

\[S_n=\frac{n(a_1+a_2)}{2}\]\[S_{24}=\frac{24(4+119)}{2}\]

Answer 18

4+5=9 would be just the second row, we don;t need to know that.

Answer 19

1476? @SolomonZelman

Answer 20

Yup!

Answer 21

Thank you!!! @SolomonZelman

Answer 22

Anytime, !