Question

For an A.P if t1= 100, tn= 1000 and n=10 find
Sn.​

Answer 1

Answer:

a = 100

an term = 1000

n = 10

an term = a + (n-1) d

1000 = 100 + 9d

d = 100

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

Sn = 10/2 ( 2× 100 + 9 × 100)

Sn = 5 ( 200 +900)

Sn = 5 ( 1100)

Sn = 5500