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2.4.4 Mean and variance of the binomial (A-level only)

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Question 31

A cereal manufacturer includes a collectible card in some of its cereal boxes. For a specific promotion, a card is placed in 30% of the boxes. No box contains more than 1 card. The boxes are sold in multipacks of 8 boxes.

a.

(i) Write down a suitable distribution to model the number of cards found in a multipack. (ii) Write down one assumption required for the model.

[2]
b.

Find the probability that in 2 randomly selected multipacks, exactly 1 multipack contains exactly 2 cards.

[3]
c.

Find the probability that a randomly selected multipack contains at least 3 cards.

[2]
d.

An organizer buys 100 multipacks for a school event.

Using a normal approximation, find the probability that more than 40 of these multipacks contain at least 3 cards.

[5]

2.4.4 Mean and variance of the binomial (A-level only) Questions

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