Question

find the sum of first 20terms of an ap in which a=1 and 20 th term = 58 ?

Answer 1

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here is u r answer@

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Solution :-

given :-

a = 1 , l = 58 , and n = 20


now , sum of 20 terms ,

S(20) = 20 /2 ( 1 + 58 ). "" [Sn = n /2 ( a + l )]


= 10 (59 )

= 590.

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Answer 2

The sum of the first 20 terms of the AP is 590

Given:

Number of terms, n = 20

First term a = 1

Last term, l = 58

To find:

The sum of the first 20 terms, $S_{20}$

Solution:

The sum of an AP, when its first and last terms are given is as follows;

$S_{n}$ = n/2 ( first term + last term ) = n/2 (a + l)

Here, n = 20

a = 1

l = 58

Therefore $S_{20}$ = 20/2 ( 1 + 58 )  = 590

The sum of the first 20 terms of the AP is 590