Question

If twelfth term of an A.P.is `30` then the sum of its third twelfth and twenty-first term is​

Answer 1

answer-

90

step by step explanation-

A12 = 30

A+11d = 30

Now, A3 + A12 + A21 = A + 2d + A + 11d + A + 20d

= 3A + 33d

= 3(A + 11d)

= 3(30)

= 90

Answer 2

Answer:

I don't know how to do it ☺️