Question

The seats at a local baseball stadium are arranged so that each row has 5 more seat 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

Answer 1

you would do an arithmetic sequence
use A1 +(n-1)d to calculate number of seats in the last row

An = 4+(24-1)5
An = 4 + (23)(5)
An = 4 + 115
An = 119 seats in the last row

now use a sum sequence to find total number of seats

Sn = n(a1 + an)/2 
Sn = 24(4+119)/2 
Sn = 24(123) /2 
Sn = 1476 total seats