Question

1,3,5,7,9 are in ap. find sn and s20

Answer 1

5n is he sn and 100 is the s20

Answer 2

1,3,5,7,9,.......

a = 1, d = 2

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

S20 = 20/2(2x1+19 x 2)
= 10(2 + 38)
= 10 x 40
= 400

Hope this helps..... Do mark my answer as brainliest..!

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@Reema