Question

The 10 th term of an a.p.is 31 and 20th term is 71. Find the 30th term

Answer 1

Step-by-step explanation:

let its first term be a

and its common difference be d

so, its 10th term is a+9d = 31

and its 20th term is a+19d =71

Subtract,

10d = 40

d=4

& a = 31-36

so, a= -5

so, its 30th term is a+29d = -5 + 116 = 111