Multiple choice

What is the average weight of girls in the class? I. Average weight of all the 60 students is 42 kg. II. Average weight of boys is 43 kg. III. Total weight of all girls together is 1144 kg.

  1. Any two of the three

  2. All I, II & III

  3. Only I & II

  4. Only II & III

  5. Question cannot be answered even with the information in all the three statements
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

We need: (Total girls' weight) / (Number of girls) = ?. Let G = number of girls. From I: Total weight = 60 x 42 = 2520 kg. Boys = 60 - G. From II: Boys' avg = 43, so boys' total = 43 x (60 - G). From III: Girls' total = 1144 kg. Using all three: 2520 = 43(60 - G) + 1144. Solving: 2520 = 2580 - 43G + 1144, 43G = 2580 + 1144 - 2520 = 1204, G = 28. Girls' average = 1144/28 = 40.85 kg (approximately 41 kg). All three statements are necessary.

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