Multiple choice

The average weight of a certain number of students in a class is 68.5 kg. If 4 new students having weights 72.2 kg, 70.8kg, 70.3kg and 66.7 kg join the class, then the average weight of all the students increases by 300 g. The number of students in the class, initially is:

  1. 21

  2. 16

  3. 11

  4. 26
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let initial students = n. Total weight = 68.5n. New total weight = 68.5n + 72.2 + 70.8 + 70.3 + 66.7 = 68.5n + 280. New average = (68.5n + 280)/(n + 4) = 68.8. Solving: 68.5n + 280 = 68.8n + 275.2, so 4.8 = 0.3n, giving n = 16. Option B is correct.

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