1.  There are three boxes each containing 3 pink and 5 yellow balls and also there are 2 boxes each containing 4 pink and 2 yellow balls. A yellow ball is selected at random. Find the probability that yellow ball is from a box of the first group?


42/61
45/61
51/61
52/61


Answer

 Option

Probability = (3/5 * 5/8)/{(3/5 * 5/8) + (2/5 * 1/3)} = 45/61

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2.  There are 4 black balls and 6 white balls. 2 balls are drawn one by one without replacement. What is the probability that the balls are same in colour?


9/21
8/17
5/14
7/15


Answer

 Option

When both black, prob.= 4/10*3/9 When both white, prob = 6/10 * 5/9 Add both cases.

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3.  Sahil has two bags (A & B) that contain green and blue balls.In the bag A, 6 green and 8 blue balls and in the bag B there are 6 green and 6 blue balls.One ball is drawn out from any of these two bags.What is the probability that the ball drawn is blue?


15/28
13/28
17/28
23/28


Answer

 Option

Total balls in Bag A = 14 balls; Total balls in bag B = 12 balls A bag= 1/2 (8c1/14c1) = 2/7 B bag = 1/2 (6c1/12c1) = 1/4 Total probability = 2/7 + 1/4 = 15/28

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4.  Out of 6 green ball, 4 blue ball, in how many ways we select one or more balls?


42
34
31
22


Answer

 Option

Explanation ; 7*5 = 35 35 - 1 = 34

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5.  One bag 6 red balls and 4 yellow balls. Four balls are picked at random what is the probability that three are red and one is yellow?


8/32
8/21
8/36
8/25


Answer

 Option

= 6c3*4c1/10c4 = 6*5*4/1*2*3*4/10*9*8*7/1*2*3*4 = 8/210 = 8/21

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