SOLUTION: find the sum of the positive two digit multiples of 3

Algebra ->  Customizable Word Problem Solvers  -> Numbers -> SOLUTION: find the sum of the positive two digit multiples of 3      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 851459: find the sum of the positive two digit multiples of 3
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
the first 2 digit multiple of three is 12
the highest is 99
an = a1 + (n - 1)d
99 = 12 + (n - 1)3
87=3n-3
90=3n
n=30 multiples
S = ½(a1 + an)n
s=1/2(12+99)*30
s=15*111
S=1665