Find the sum of first 20 terms of the series 7 + 7.7 + 7.77 +.... – InterviewSolution

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1.

Find the sum of first 20 terms of the series 7 + 7.7 + 7.77 +....

Answer»

a=7

d=7.7-7=0.7

an=?

n=20

an=a+(n-1) d

an=7+(20-1) 0.7

an=7+19*0.7

an=7+13.3

an=20.3

SUM=n/2(a+l)

=20/2(7+20.3)

=10*27.3

Hence the sum is 273

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