Question

The number of terms of the ap is 2 and common difference is 4 then sum of its 40 terms is

Answer 1

Answer:

n=2, d=4, Sn= 40

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

S2= 2/2 [2a+(2-1) 4]

40 = 1 ( 2a + 1×4)

40 = 2a +4

40 - 4 = 2a

36 = 2a

36/2 = a

18 = a

Answer 2

In the AP, a = 2, d = 4 and n = 40, hence

The sum of 40 terms is (it is not the sum of the 40th term)

S40 = (40/2)[2*2 + (40–1)*4]

= 20[4+ 156]

= 20*160

= 3200.