Question

Determine a soma dos termos da P.A finita (6,10,14...,154)

Answer 1

an = a1+(n-1).r
154 = 6+(n-1).4
154 = 6+4n-4
156/4 = n
n = 39

sn =( a1+an).n/2
sn = (6+154)39/2
sn = 2.886