Find the sum on terms

Question

find the sum of the terms in the sequence 1,4,7,...,193.

Answer 1

193 = 1 + (n - 1)3

192 = 3n - 3

195 = 3n

65 = n

 

S₆₅ = (65/2)(1 + 193)

S₆₅ = (65/2)(194)

S₆₅ = (65)(97)

S₆₅ = 6305