Question

first term and common difference of AP are 6 and 3 respectively find s

Answer 1

The AP is going to be 6,9,12,15,18...
if you want to find Sn then use this:

n/2{2a+(n-1)d}

and if you know the last number then use this:

n/2{a+an}

HOPE THAT HELPED YOU

Answer 2

Solution:   a = 6, d = 3,  S27S27 = ?

       SnSn = n2[2a+(n−1)d]n2[2a+(n−1)d]

      S27S27 = 272[2∗6+(27−1)3]272[2∗6+(27−1)3]

      S27S27 = 272[12+(27−1)3]272[12+(27−1)3]

      S27S27 = 272[90]272[90]                              [∴ 12 + 26 × 3
                                                               = 12 + 78 = 90]

       S27S27 =  27 × 45

              =  1215 

I Hope It Will Help!

^_^