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Q: The average weight of a certain number of students in a group is 72 kg. If 10 students having an average weight of 78 kg leave and 4 students having an average weight of 80 kg join the group, the average weight of the students in the group decreases by 0.7 kg. The number of students initially in the group is :
  • A. 54
  • B. 46
  • C. 56
  • D. 44
Correct Answer: Option B - Let the total number of student = x Total weight = 72x According to the question, Total weight = 71.3 × (x – 6) 72x – 780 + 320 = 71.3x – 427.8 0.7 x = 460 – 427.8 = 32.2 x = 46
B. Let the total number of student = x Total weight = 72x According to the question, Total weight = 71.3 × (x – 6) 72x – 780 + 320 = 71.3x – 427.8 0.7 x = 460 – 427.8 = 32.2 x = 46

Explanations:

Let the total number of student = x Total weight = 72x According to the question, Total weight = 71.3 × (x – 6) 72x – 780 + 320 = 71.3x – 427.8 0.7 x = 460 – 427.8 = 32.2 x = 46