Question

Find the sum of



a.P. Series where n=14.



3, 8,13,18,....?

Answer 1

hey.

Here a(first no) = 3,
=) d(common diff) = 8-3

= 5.

since Sn = n/2[2a + (n-1)d]

= 14/2 [2(3) + (14-1)5]

= 7[6 +13(5)]

= 7(6+65)

= 7*71

= 497

hope it helps you!!

Answer 2

Answer:

497

Step-by-step explanation:

Given:- 3, 8,13,18,.... where n=14.

To Find:- Sum of the above A.P.

Solution:- 3, 8,13,18,.... is an A.P., where first term = 3,

                                                      common difference = 5,

                                                      number of terms = 14

As we know, last term = first term + (n -1)c.d.

⇒ last term = 3 + (14 - 1)5

                   = 3 + 13 × 5

                   = 3 + 65

                   = 68

As we know, Sum of all terms = n/2 (first term + last term)

                                                  = 14/2 (3 + 68)

                                                  = 7 × 71

                                                  = 497

Therefore, Sum of the A.P. is 497.

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