Multiple choice

A box contains 20 electric bulbs, out of which 5 are defective. Two bulbs are chosen at random from this box. The probability that at least one of these is defective is

  1. 1/4

  2. 17/38

  3. 21/38

  4. 3/38

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

P (none of the balls is defective) = 15C2/20C2

                                                         = 21/38

P(at least one ball is defective) = 1 - 21/38

                                                    = 17/38

 

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