Question

Q.20 Find the sum of first 22 terms of an A.P.in which
d=7 and 22" term is 149.
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Answer 1

Hola mate!! here is ur ans;

We have; n = 22, d = 7 and a22 = 149

where n is number of terms and

d is common difference.

We know;

an = a + (n – 1)d

⇒ 149 = a + (22 - 1)7⇒ 149 = a + 147⇒ a = 149 - 147⇒ a = 2

The sum can be calculated as follows:

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

22/2 ×(2+149)

= 11*151

= 1661

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Answer 2

Answer:

a22=a+21d

149=a+21*7

149-147=a

2=a

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

S22=22/2[2*2+(22-1)*7]

=11[4+21*7]

=11*151

S22=1661