20th term= 119
Step-by-step explanation:
Let the first term of AP be a
and common difference be d
nth term is given by,
= a+(n-1)d
6th term = 35
a+(6-1)d= 35
a+5d=35 -----------------(i)
13th term = 77
a+12d= 77----------------(ii)
Now, equation (ii) - (i)
a+12d-(a+5d)= 77-35
a+12d-a-5d= 42
7d=42
d=6
Now, from equation (i)
a= 35-5d= 35-5(6)= 35-30 = 5
20th term= a+19d= 5+19(6)= 119
