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

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Question 39

The life of a certain type of battery, BBB hours, is normally distributed with a mean of 120 hours and a standard deviation of 16 hours.

a.

Find P(B>144)P(B > 144)P(B>144).

[2]
b.

Find the value of kkk such that P(B<k)=0.15P(B < k) = 0.15P(B<k)=0.15.

[3]
c.

Ben is preparing for a 12-hour recording session. Given that the battery has already been in use for 144 hours,

find the probability that the battery will not run out before the session is completed.

[4]

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

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