Question

Find the Sum if the AP's 2 , 7 , 12 , 17 ...... to 19 terms

( Use the formula ) =
$sn \: = \: \frac{n}{2} ( \: a \: + \: l)$

Answer 1

Here a=2,d=5
L=2+(19-1)5
=2+18×5
=2+90
=92
Sum=n/2(a+l)
=19/2(2+92)
= 19×94/2
= 893

The sum of the given ap is 893

Answer 2

Hi

Here is ur answer

Given:

n = 19  a = 2  d = 7-2 = 5

To find the last last term substitute given value in the following equation:

Tn = a + ( n- 1) d

    = 2 + ( 19 -1 ) 5

    = 2 + 18 ×5

    = 2 + 90

   Tn = 92

Given:

l = Tn = 92     n = 19   a =2

To get the sum of those terms in the sequence substitute the given values in the following equation:

$Sn = n/2 ( a+l)$

           = 19/2(2 + 92)

           = 19/2 (94)

           = 19×47

          Sn = 893

Hope it helps U