A) 10
B) 11
C) 12
D) 13
Correct Answer: A
Solution :
\[\frac{31}{42}=\left( \frac{n}{2n+1} \right).1+\frac{(n+1)}{(2n+1)}.\frac{1}{2}\] \[\Rightarrow (31).2(2n+1)=42(2n+n+1)\] \[\Rightarrow 31(2n+1)=21(3n+1)\] \[\Rightarrow 62n+31=63n+21\] \[\Rightarrow n=10\]You need to login to perform this action.
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