math
posted by Anonymous on .
Find the sum of the first 33 terms of the arithmetic sequence whose first term is 3 and whose 33rd term is 253

As you (should) know,
Sn = n/2 (a1 + an)
S33 = 33/2 (a1 + a33)
= 33/2 (3  253)
= 33/2 (250)
= 33*125 = 4125