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Question

The sum of first 9 terms of the series 131+13+231+3+13+23+331+3+5+ is

A
71
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B
96
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C
142
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D
192
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Solution

The correct option is B 96
Given series is 131+13+231+3+13+23+331+3+5+
Let Tn be the nth term of the given series.
Tn=13+23+33++n31+3+5++upto n terms
={n(n+1)2}2n2=(n+1)24
S9=9n=1(n+1)24=14(22+33++102)+124124
=14[10(10+1)(20+1)61]=3844=96

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