Quality-control probabilities and added items

Quality-control probabilities and added items

Secondary 2
5 marks
TGM Original Questions

Core stretch

A factory packs 3600 cereal boxes. The probabilities that a box is underweight and overweight are \(\frac{1}{12}\) and \(\frac{1}{18}\), respectively. One box is selected at random.

  1. Find the probability that a box has the exact mass.[2]
  2. Find the number of overweight boxes.[1]
  3. Exact-mass boxes are added until the exact-mass probability is \(\frac{9}{10}\). Find how many are added.[2]

Solution:

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Answer:(a) \(\frac{31}{36}\) (b) \(200\) (c) \(1400\).

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