MathematicsA bag contains 15 balls, out of which some are white and the others are black. If the probability of drawing a black ball at random from the bag is 2 3 ,   then find how many white balls are there in the bag.

A bag contains 15 balls, out of which some are white and the others are black. If the probability of drawing a black ball at random from the bag is 2 3 ,   then find how many white balls are there in the bag.


  1. A
    2
  2. B
    3
  3. C
    6
  4. D
    5 

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    Solution:

    It is given that a bag contains 15 balls, out of which some are white and the others are black. Also the probability of drawing a black ball at random is 2 3  .
    So, the total number of balls is 15.
    Total favorable outcomes = probability of blackball + probability of white ball
    Total favorable outcomes = 1
    Probability of white ball = 1 - the probability of the black ball
    Probability of drawing a white ball =1 2 3  
    Probability of drawing a white ball = 1 3  
    The formula of the probability of an event is the number of favorable outcomes divided by the total number of outcomes.
    Let E be an event that the ball drawn is white.
      P(E)= no. of favorable outcomes   total number of outcomes   
    Substituting the values,
    1 3 = no. of favorable outcomes   15   
    no. of favorable outcomes =15× 1 3  
    no. of favorable outcomes = 5
    Therefore, the number of white balls is 5  .
    Hence, the correct option is 4.
     
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