The sum of the first 20 terms of the A.P. 1, | vedclass

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(A) The given $A.P.$ is $1, 21, 41, \ldots$Here,the first term $a = 1$.The common difference $d = 21 - 1 = 20$.The number of terms $n = 20$.The formul

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$3820$

Vedclass · Answer

(A) The given $A.P.$ is $1, 21, 41, \ldots$Here,the first term $a = 1$.The common difference $d = 21 - 1 = 20$.The number of terms $n = 20$.The formula for the sum of the first $n$ terms of an $A.P.$ is $S_n = \frac{n}{2} [2a + (n - 1)d]$.Substituting the values: $S_{20} = \frac{20}{2} [2(1) + (20 - 1)20]$.$S_{20} = 10 [2 + (19 	imes 20)]$.$S_{20} = 10 [2 + 380]$.$S_{20} = 10 [382]$.$S_{20} = 3820$.Therefore,the sum of the first $20$ terms is $3820$.

The sum of the first $20$ terms of the $A.P.$ $1, 21, 41, \ldots$ is:

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