A) 18
B) 16
C) 15
D) 14
Correct Answer: C
Solution :
Sol. |
Number of children in camp = x |
Total weight of children = 20x |
Now according to question, |
Average when 5 children of weight 12 kg join the |
the camp |
\[=\frac{20x+60}{x+5}\] |
And average when 10 children of weight 21 kg leave the camp |
\[=\frac{20x-210}{x-10}\] |
\[\Rightarrow \,\frac{20x+60}{x+5}\,=\,\frac{20x-210}{x-10}\] |
\[\begin{align} & \Rightarrow \,20{{x}^{2}}\,+60x\,-200x\,-600\,=200{{x}^{2}} \\ & -210x+100x-1050 \\ & -140x-600=-100x-1050 \\ \end{align}\] |
\[30x=450\Rightarrow x=15\] |
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