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# Probability problem

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 intermediate(ipc)course no [ Scorecard : 1449] Posted On 28 July 2012 at 18:12 1. x & y stand in a line with 6 other people.what is the probability that there are 3 persons between them ? ans is 1/7,how? 2. four digits 1,2,4 & 6 are selected at random to form a four digit number.what is the probability that the number so formed,would be divisible by 4? ans is 1/3,how? 3. a packet of 10 electronic components is known to include 3 defectives.if 4 components are selected from the packet at random,what is the expected value of the number of defective? ans is 1.20,how? !..SaNKeT..! !..Live to Give..! [ Scorecard : 14364] Posted On 28 July 2012 at 18:16 1. Let us write down all the possibilities: In all there are 8 persons. Let us put X at top position and Y at 5 th position. Similarly, take X to 2,3,4 positions. We can reverse these positions also. Thus there are 8 possibilities. In all X and Y have 8*7 possibilities, so 8 /56 is the answer. and it is 1/7.....

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