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2.4.8 Normal distribution as a model (A-level only)

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Question 16

A shipping facility handles two types of cargo boxes: Premium, PPP, and Economy, EEE. The masses, in grams, of Premium boxes are distributed as P∼N(850,302)P \sim \text{N}(850, 30^2)P∼N(850,302) and Economy boxes are distributed as E∼N(600,252)E \sim \text{N}(600, 25^2)E∼N(600,252).

A Premium box and an Economy box are selected at random.

a.

Find the probability that the mass of the Premium box is less than 140% of the mass of the Economy box.

[3]
b.

Two Premium boxes are chosen at random.

Find the probability that their masses differ by more than 45 g.

[3]
c.

The facility ships boxes on heavy-duty pallets. Each pallet contains either 6 Premium boxes or 8 Economy boxes. The mass of an empty pallet, WWW, is distributed as W∼N(2000,1002)W \sim \text{N}(2000, 100^2)W∼N(2000,1002).

Find the probability that a pallet of 8 Economy boxes has a greater total mass than a pallet of 6 Premium boxes.

[5]

2.4.8 Normal distribution as a model (A-level only) Questions

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