What is the average weight of boys in the class? I. Average weight of all the 60 students is 45 kg. II. Average weight of girls is 50 kg. III. Total weight of all the boys together is 1250 kg.
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Only II and III
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I and either II or III
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Any two of these
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All I, II and III
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Cannot be determined
D
Correct answer
Explanation
From statement I: Total weight of 60 students = 60 × 45 = 2700 kg. From statement III: Total weight of boys = 1250 kg. So weight of girls = 2700 - 1250 = 1450 kg. From statement II: Average weight of girls = 50 kg, so number of girls = 1450/50 = 29. Number of boys = 60 - 29 = 31. Average weight of boys = 1250/31 ≈ 40.32 kg. All three statements are needed.