Question

what is the value of n for an A.P if t1=2 ,tn =41 ,and Sn=860

Answer 1

Answer:

given, Sn=860

and a =t1 =2

L=tn =41

By using formula Sn=n/2[a +L]

860=n/2[2+41]

860=43n/2

860×2=43n

1720= 43n

or n=1720/ 43

then, n=40

the value of n is 40

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