In arithmetic progressions of exercise 5.3 of math, how i solve this important question in best way, please help me for solving this problem Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149.

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# Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149. Q.7

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Given,

Common difference, d = 7

22

^{nd}term, a_{22}= 149Sum of first 22 term, S

_{22}= ?By the formula of nth term,

a=_{n}a+(n−1)da_{22}=a+(22−1)d149 =

a+21×7149 =

a+147a= 2 = First termSum of n terms,

S=_{n}n/2(a+a)_{n}S= 22/2 (2+149)_{22}= 11×151

= 1661