General Aptitude - 34.1 Probability - General Questions Free Online Tests | Mock Tests | Preparation | Practice Tests

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A bag contains 4 white, 5 red and 6 blue balls. Three balls are drawn at random from the bag. The probability that all of them are red, is:

A. 1/22

B. 3/22

C. 2/91

D. 2/77

E. None of the above

View Answer

Correct choice: C

Explanation:

Let S be the sample space.

Then, n(S)

= number of ways of drawing 3 balls out of 15

= ¹⁵C₃

=	(15 x 14 x 13)
	(3 x 2 x 1)

= 455.

Let E = event of getting all the 3 red balls.

∴ n(E) = ⁵C₃ = ⁵C₂ =

(5 x 4)/(2 x 1)

= 10.

∴ P(E) =

n(E)/n(S)

10/455

2/91.

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