A batch of 25injectionmolded parts contains five that have s

A batch of 25-injection-molded parts contains five that have suffered excessive shrinkage. If two parts are selected at random, and without replacement, what is the probability that the second part selected is one with excessive shrinkage?

Solution

Suppose P is the probability that a part cannot suffered with excessive shrinkage than

P= 20/25

and P\' is the  probability that a part can suffered with excessive shrinkage than

P\'= 5/25

Now we have to find The probability of that the second selected part is suffered with excessive srinkage

Means first part can suffer srinkage or can not suffer shrinkage.

In first case when first part can not suffer shrinkage and second part suffer shrinkage

Probability of first part can not suffer shrinkage and second part suffer shrinkage=P₁= 20/25* 5/24 ( without replacement)

Now probability of that first part can suffer shrinkage and second part also suffer shrinkage =P₂ = 5/25*4/24

Than the required probability

P(second part suffer shrinkage)= P₁+ P₂= 20/25*5/24+5/25*4/24= 0.2