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ICSE-VIII-Mathematics

23: Probability Class 8 Maths

with Solutions -
Qstn# 7 Prvs-QstnNext-Qstn
  • #7
    A bag contains 3 white, 5 black and 2 red balls, all of the same shape and size.
    A ball is drawn from the bag without looking into it, find the probability that the ball drawn is: (i) (a) black ball. (ii) (a) red ball. (iii) (a) white ball. (iv) not a red ball. (v) not a black ball.
    Ans : In a bag, 3 balls are white
    2 balls are red
    5 balls are black
    Total number of balls = 3 + 2 + 5 = 10 (i) Numbers of possible outcome of one black ball = 10
    And number of favourable outcome of one black ball = 5
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 5/10
    = 1/2 (ii) Number of possible outcome of one red ball = 10
    And number of favourable outcome = 2
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 2/10
    = 1/5 (iii) Number of possible outcome of white ball = 10
    And number of favourable outcome = 3
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 3/10 (iv) Number of possible outcome = 10
    Number of favourable outcome = 3 + 5 = 8
    Not a red ball
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 8/10
    = 4/5 (v) Number of possible outcomes = 10
    Number of favourable outcome not a black ball = 3 + 2 = 5
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome) = 5/10
    = 1/2
  • #7-i
    (a) black ball.
    Ans : Numbers of possible outcome of one black ball = 10
    And number of favourable outcome of one black ball = 5
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 5/10
    = 1/2
  • #7-ii
    (a) red ball.
    Ans : Number of possible outcome of one red ball = 10
    And number of favourable outcome = 2
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 2/10
    = 1/5
  • #7-iii
    (a) white ball.
    Ans : Number of possible outcome of white ball = 10
    And number of favourable outcome = 3
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 3/10
  • #7-iv
    not a red ball.
    Ans : Number of possible outcome = 10
    Number of favourable outcome = 3 + 5 = 8
    Not a red ball
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome)
    = 8/10
    = 4/5
  • #7-v
    not a black ball.
    Ans : Number of possible outcomes = 10
    Number of favourable outcome not a black ball = 3 + 2 = 5
    ∴ P(E) = (Number of favourable outcome)/(Number of all possible outcome) = 5/10
    = 1/2