Question

if the sum of first 10 terms of an AP is 1050 and its first term is 5. Find the 20 th term and sum of first 20 terms.​

Answer 1

Given,

S_10 = 1050

a = 5

a_20 = ?

S_20 = ?

S_10 = 10/2[2x5 + 9d]

1050 = 5(10+9d)

210= 10 +9d

d = 200/ 9

a_20 = 5+19 x 200/ 9

or, 5+422.2

or, 427.2

S_20 = 10(10+19x200 / 9)

0r, 10(10 + 422.22)

0r, 4322.2