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the 3rd term of an A.P is 6 and the 16th term is 32 find the common difference and the sum of the first 20 term

 Jul 18, 2020
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6 + thirteen d's = 32

13d = 26

d = 2         

3rd term is 6   next is  8     10    12   14  16  18 20  22 24 26  28 30 32=16th term

 

1st term is   6 - 2 -2 = 2

Sumn = n/2 (a1 + an)

          = 20/2 (2 + 40) = 420

 Jul 18, 2020

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