Ten percent of the engines manufactured on an assembly line are defective. If engines are randomly selected one at a time and tested, what is the probability the fourth defective engine will be found on the second trial?

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Step-by-step explanation:

From the given information;

Let x be the number of trails on which the defective occurs.

Let the probability that an occurrence of a defective be p = 0.10

Suppose x is a random variable that follows a negative binomial distribution with parameters r and p.

Then the probability mass function of X can be expressed as:

We are to find the probability of the fourth defective engine will be found on the second trial.

i.e. r =  4 and x = 2

i believe the correct answer is option 4.principalities were small territories that were run by russian rulers.

which statement correctly defines principalities in northern asia in the 1200s? principalities were small territories that were run by russian rulers.

hope i could ! : )