Question

Three screws are drawn at random from a lot of 50 screws, 5 of which are defective. Find the
probability of the event that all 3 screws are non-defective, assuming that the drawing is
(a) with replacement (b) without replacement​

Answer 1

Answer:

options (d) right answers

Answer 2

$\huge{\tt{\color{pink}{QuesTion :}}}$

Three screws are drawn at random from a lot of 50 screws, 5 of which are defective. Find the

probability of the event that all 3 screws are non-defective, assuming that the drawing is

(a) With replacement

(b) Without replacement

$\huge{\tt{\color{blue}{SoluTion :}}}$

Total screws = 50

Defective screws = 5

Non-defective screws = 50-5 = 45

Let A be the event of getting drawing of 3 screws are non-defective.

(a) With replacement :

$P(A) = \frac{45C}{50C} × \frac{45C}{50C} \times \frac{45C}{50C} \\ = > (\frac{9}{10} )³$

(b) Without replacement :

$P(A) = \frac{45C}{50C} \times \frac{44C}{49C} \times \frac{43C}{48C} \\ = > \frac{45}{50} \times \frac{44}{49} \times \frac{43}{48} \\ = > \frac{1419}{1960}$

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