A group of five persons is formed from five boys and four girls. Find the probability that there are at least two girls in the group?
Total number of possible ways =
9C5 = 9 x 8 x 7 x 6 x 55 x 4 x 3 x 2 x 1 = 126
Number of favorable cases =
4C2 x 5C3 + 4C3 x 5C2 + 4C4 x 5C14 x 32 x 1 x 5 x 4 x 33 x 2 x 1 + 4 x 3 x 23 x 2 x 1 x 5 x 4 2 x 1 + 1 x 5= 6 x 10 + 4 x 10 + 5= 60 + 40 + 5= 105
Therefore, required probability = 105/126 = 5/6
If the standard deviation of 0, 1, 2, 3 ......... 9 is K, then the standard deviation of 10, 11, 12, 13 ........... 19 will be:
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