Question
A box contains 20 electric bulbs , out of which 4 are defective . Two bulbs are chosen at random from this box.The probability that at least one of these is defective is :
Answer: Option B
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P (None is defective ) = `(16_(C_2))/(20_(C_2)) = ((16 xx 15)/(2 xx 1) xx (2 xx 1)/(20 xx 19)) = 12/19`
P ( at least one is defective ) = `(1 - 12/19) = 7/19`
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