Question

the first term of an ap is 3 and the sum of first five terms is 1/11th of the sum next five terms
find the 20th term

Answer 1

assume the terms as a-2d,a-d,a,a+d,a+2d,...and
so on
where a is first term
d is common difference
sum of five terms =5a from the above
and a=3 from the question
from the given condition in the question
5a=1÷11(next sum of five terms)
5×3=1÷11(a+3d+a+4d+......a+7d)
15=1÷11(5a+25d)
15×11=5×3+25d
165-15=25d
d=6
20 th term is a+17d=3+17×6=105