Question

Out of 100 screws 70 are good and 30 are defective. Find the probability that out of 2 screws selected at random 1) Both are good 2) First good and second defective

Answer 1

hey mate iam only able to explain 1 st case sorry

Answer 2

Concept

The probability of any event tell the approximate possible outcome of any events to occur in the nature. Suppose n(E) is the number of occurrence of event E from the total outcome n(N), therefore the probability for occurrence of event E is defined as,

P=n(E)/n(N)

And also two independent event are multiplied to get the net probability.

Given

Total number of screw = 100

The number of good screw = 70

The number of defective screw = 30

Find

We have to calculate the probability of getting two good screw and the probability of getting one good and one defective.

Solution

The probability of getting one good screw P1 = 70/100

P1  = 7/10

The probability of getting one defective screw P2 = 30/100

P2 = 3/10

1) The probability of getting both screw good when picked at the same time = 7/10 * 7/10

= 49/100

2) The probability of getting one good and one defective when picked both at the same time = 7/10 * 3/10

= 21/100

Hence the probability of the two events are 49/100 and 21/100.

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