Probability – Exercise – 1

31. A die is tossed twice. Getting a number greater than 4 is considered a success. Then the variance of the probability distribution of the number of successes is :

(a) 2/9
(b) 4/9
(c) 1/27
(d) none of these

32. Three groups of children contain respectively 3 girls & 1 boy,2 girls & 2 boys, 1 girl & 3 boys. One child is selected at random from each group. The chance that three selected consisting of 1 girl & 2 boys, is :

(a) 9/32
(b) 3/32
(c) 13/32
(d) none of these

33. A bag contains 3 white, 3 black and 2 red balls. One by one three balls are drawn without replacing them. The probability that the third ball is red, is :

(a) 1/2
(b) 1/3
(c) 2/3
(d) 1/4

34. The probability that a man can hit a target is 3/4 . He tries 5 times. The probability that he will hit the target atleast three times, is :

(a) 291/364
(b) 371/464
(c) 471/502
(d) 459/512

35. Three of the six vertices of a regular hexagon are chosen at random. The probability that the triangle with these 3 vertices is equilateral, is equal to :

(a) 1/2
(b) 1/5
(c) 1/10
(d) 1/20

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