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  4. In an arithmetic sequence, the sum of first and third terms is 6 and the sum of second and fourth terms is 20 Then the 11 text th term is

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Q. In an arithmetic sequence, the sum of first and third terms is $6$ and the sum of second and fourth terms is $20$ Then the $11^{\text {th }}$ term is

KEAMKEAM 2020

Solution:

$a+a+2 d=6$
$2 a+2 d=6$
$a+d=3 ...(1)$
$a+d+a+3 d=20$
$2 a+4 d=20$
$a+2 d=10 ...(2)$
$d=7, a=-4$
$T_{11}=-4+70=66$