Question

Quantos termos tem a P.A. (15, 20, 25, ..., 160)?

Answer 1

an= a1+( n-1).r

160= 15+( n-1)  5
160= 16+5n-5
160-16+5=5n
5n= 150
n= 150:5
n=30   Pa tem 30 termo