What will be the total average weight of all children in school? Statement I: The average weight of boys in school is 55 kg. Statement II: The average weight of girls in school is 49 kg. Statement III: The number of boys in the school is 30% more than the number of girls.
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Only III
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All of the necessary
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Only II and III
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Only I and II
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None of the above
B
Correct answer
Explanation
To find total average weight, we need weighted average: (total boys weight + total girls weight) / (total boys + total girls). Statement I gives boys' average = 55. Statement II gives girls' average = 49. Statement III gives boys = 1.3×girls. Using all three: Let girls = g, boys = 1.3g. Total average = (55×1.3g + 49×g) / (1.3g + g) = (71.5g + 49g) / 2.3g = 120.5/2.3 ≈ 52.4 kg. All three statements are necessary.