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?

these are the choices
1,476
2,856
2,952
1,428

You can use the arithmetic sequence equation. This will tell you the number of seats in the last row

An = A1+ (n-1)d 

An = 4+(24-1)5 
An = 4 + (23)(5) 
An = 4 + 115 
An = 119 

Then, you take that answer and plug it to this equation: Sn = n(a1 + an)/2 

Sn = 24(4+119)/2 
Sn = 24(123) /2 
Sn = 1476