Question

Find the sum of of the A.P. 500, 520, 540 up to 84 terms.​

Answer 1

Answer:

a=500

d=20

an=a+(n-1)d

a84=500+(84-1)20

      =500+83x20

a84=2160=L

sn=n/2(a+L)

   =84/2(500+2160)

sn=111720