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+3 votes
A batch of one hundred bulbs is inspected by testing four randomly chosen bulbs. The batch is rejected if even one of the bulbs is defective. A batch typically has five defective bulbs. The probability that the current batch is accepted is__________.
in Numerical Ability by Boss (30.7k points) | 1.6k views

2 Answers

+7 votes
Best answer
In a batch there are total $100$ bulbs of which
$95$ are working
$5$ are defective.

$P$(Selecting $4$ working bulbs)$ = \dfrac{95}{100}\times \dfrac{94}{99}\times \dfrac{93}{98}\times \dfrac{92}{97}= 0.81$
by Loyal (9.7k points)
edited by
by default is without replacement

Hi @rajan,

Actually we are choosing in one go ->

So P(Selecting 4 working bulbs) = $\frac{\binom{95}{4}}{\binom{100}{4}}$

In selected answer bulbs are selected one by one ..but it is not given

we should take P(Selecting 4 working bulbs out of 100) = $\binom{95}{4} / \binom{100}{4}$
+4 votes

Apologies, please bear with the wrong orientation.

by (167 points)

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