intermediate(ipc)course (no) (1460 Points)
28 July 20121. 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..!)
(16427 Points)
Replied 28 July 2012
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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