1.  A bag contains 3 red balls and 8 black balls and another bag contains 5 red balls and 7 black balls, one ball is drawn at random from either of the bag, Find the probability that the ball is red?


93/264
95/264
91/264
97/264


Answer

 Option

probability = probability of selecting the bag and probability of selecting red ball (1/2) * (3/11) + (1/2) * (5/12) = 91/264

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2.  A bag contains 3 red balls and 8 black balls and another bag contains 5 red balls and 7 black balls, one ball is drawn at random from either of the bag, Find the probability that the ball is red?


91/264
97/264
98/264
95/264


Answer

 Option

(1/2) * (3/11) + (1/2) * (5/12) = 91/264

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3.  A bag contains 8 blue and 7 green balls. 2 balls are drawn one by one without replacement. What is the probability that the balls are alternately of different colors?


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


Answer

 Option

When 1st is blue, prob = 8/15 * 7/14 when 1st is green, prob = 7/15 * 8/14 Add both cases.

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4.  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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5.  A bag contains 3 red, 4 green and 3 yellow balls. if 2 balls are drawn at random. What is the probability that they are of different color?


9/16
4/15
12/45
5/11


Answer

 Option

This will be = 1 - prob. (Both are same in colour) Prob. of both same in colour = (3c2+4c2+3c2)/10c2 = 12/45 So, required prob = 1 - 12/45

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