Question

Which term of the ap 3,15,27,39...wil be 129more then its 21th term

Answer 1

Answer:

Step-by-step explanation:

a = 3

d= 12

T21= a + (21-1)d

= 3 +20×12

=243

Now Tn= 243+ 129

=> a+(n-1)d = 372

=> 3+(n-1)×12 =372

=> (n-1)×12 = 372 - 3 = 369

=> n-1 = 369/12 = 123/4

=> n = (123/4)+ 1 = 127/ 4

=> n is not a positive integer. Hence there is no such term in the gven A. P which is 129 more than its 21th term.