Question

Which term of the A.P.3, 15, 27, 39, ... will be 120 more than its 21st term?​

Answer 1

Answer:

Step-by-step explanation:

let find 21st term

in A.P d=12

a=3

n=21

21st term

=a+(n-1)d

=3+20x12

=243

add 120 to 21st term

=243+120

363

let find which is that

363=3+(n-1)12

360=12(n-1)

30=n-1

n=31