posted by jessica on .
a grocery store display consists of cases of soda. there are 15 cases at the base, and 1 case at the top. if there are 15 rows, how many cases are needed for the entire display? a) 180 b)30 c)130 d)15
looks like an arithmetic series
sum of terms of AS = (n/2)(first + last)
= (15/2)(15+1) = 120
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15 = 120