Question

find the sum of first 20 terms of an AP.whose first term is 3 andthe last term is 57.

Answer 1

Hi Friend !!!

Here is ur answer !!!


Sn = n/2 (a+an)

S20 = 20/2 (3+57)

S20 = 10(60)

S20 = 600


Hope it helps u : )

Answer 2

Heya !!!


First term ( A) = 3



And,



Last term ( L) = 57



Therefore,



Sn = N/2 × ( A + L)



S20 = 20/2 × ( 3 + 57)





=> 10 × ( 60)




=> 600


HOPE IT WILL HELP YOU....... :-)