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From a bag containing 8 white and 5 Black balls. Four balls are drawn one by one without replacement . Find the probability that exactly two of them are white.

Asked by sachinkumarmishra1 | 23 Jan, 2020, 12:00: PM
Total number of balls = 8+5 = 13
4 balls are drawn at random out of which exactly two balls are white, so the remaining two balls are black
1st ball can be drawn in 13C1 no. of ways
Only 12 balls are left, so the 2nd ball can be drawn in 12C1 no. of ways
Only 11 balls are left, so the 3rd ball can be drawn in 11C1 no. of ways
Only 10 balls are left, so the 4th ball can be drawn in 10C1 no. of ways
So, the total number of ways of drawing 4 balls = 13C112C111C110C1
No of ways such that exactly 2 balls are white = 8C1 x 7C1
No of ways such that exactly 2 balls are black = 5C1 x 4C1
Answered by Renu Varma | 24 Jan, 2020, 10:31: AM

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