Arithmetic progression

Question

if 9th term of an AP is 0, then ratio between 29th and 19th term is

 

Answer 1

Let the first term be a, the common difference d.

the ninth term is a+8d=0, which makes a=-8d

The ratio of the 29th term to the 19th term is

(a+28d)/(a+18d)=20d/10d=2