If copies of all your computer data are stored on four independent hard disk​ drives, what is the probability that during a​ year, you can avoid catastrophe with at least one working​ drive? With four hard disk​ drives, the probability that catastrophe can be avoided is

Step-by-step explanation:

Given

--- rate of hard disk drives failure

--- number of hard disk drives

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Required

First, calculate the probability that the none of the 4 selected is working;

Using the complement rule, the probability that at least 1 is working is:

This gives:

2 x^2 -3x+p

sum of roots = 3/2

let other root be x

3+ x = 3/2

x= 3/2 - 3 = -3/2

product of roots = p/2

3× -3/2 = p/2

-9 = p

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