Question

A box contains 20 lightbulbs, of which 5 are defective.

If 4 lightbulbs are picked from the box randomly, the probability that at most 2 of them are defective is ________?

Answer 1

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Answer 2

The probabilities of 0, 1 and 2 defectives need to be calculated and added.
\[\large P(0)=\frac{15C4}{20C4}\]
\[\large P(1)=\frac{5C1\times 15C3}{20C4}\]
\[\large P(2)=\frac{5C2\times 15C2}{20C4}\]

Answer 3

okay thanks :) i think i got it from here

Answer 4

Let me know if your need more help on this.