Question

Find the sum of the first twelve terms of an A.P whose nth term is 3n+4​

Answer 1

Answer:

282

Step-by-step explanation:

To find the sum of arithmetic sequence:

 Find the first and last term.

    nth term = 3n + 4

First term = a = 3*1  + 4

                      = 3 + 4

                      = 7

Last term =  l = 3*12 + 4

                     = 36 + 4

                     = 40

$\sf \boxed{\bf S_n = \dfrac{n}{2}(a +l)}$

         $\sf = \dfrac{12}{2}(7 + 40)\\\\ =\dfrac{12}{2}*47\\\\ = 6 * 47\\\\ = 282$