Multiple choice general knowledge math & puzzles

A box contains 20 bulbs, out of which 4 are defective. If we randomly choose 2 bulbs from this box, wht will be the probability that atleast 1 bulb is defective.

  1. 4/19

  2. 7/19

  3. 12/19

  4. 21/95

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Use the complement: P(at least 1 defective) = 1 - P(no defective) = 1 - P(both good). P(both good) = (16/20) * (15/19) = 240/380 = 12/19. So P(at least 1 defective) = 1 - 12/19 = 7/19.