Math, asked by sujalkhaire1920, 1 month ago

the first term of an A.P is 1 and the nth term is 20.if Sn=339,what is n=?

Answers

Answered by inzy97

2

Answer:

sn=n/2(a+an)

339=n/2(1+20)

339=21n/2

2*339=21n

678=21n

n=678/21

n=32.28

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