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JEE Main201911 Jan 2019Evening ShiftMathematicsProbabilityActual

A bag contains 30 white balls and 10 red balls. 16 balls are drawn one by one randomly from the bag with replacement. If X be the number of white balls drawn, then ( mean of X standard deviation of X ) is equal to:

Options

  1. A4
  2. B4 3
  3. C3 2
  4. D4 3 3

Correct answer

B. 4 3

Step-by-step solution

P( white ball )= 30 40 = 3 4 , Q (red ball) = 10 40 = 1 4 , n=16 Mean of X standard deviation of X = n P n P Q = n P Q = 16 3 4 1 4 = 48 =4 3

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