Answer:
20,667.
Step-by-step explanation:
This is an arithmetic series:
3 + 9 + 15 + 21 + 27+ ...........+ 495
First term = 3 and common difference = 6.
Number of terms = ( 495 - 3 )/6 + 1
= 83.
So Sn = n/2(a1 + l) where a1 = first term and l = last term
S83 = 83/2(3 + 495)
= 41.5 * 498
= 20,667.
