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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 Jun 2008 11:18:05 IST
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(1) a three digit no. is choosen at random . find the probability that a three digit choosen no. has exactly 3 factor.
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22 Jun 2008 11:26:30 IST
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If it has 3 factors, then it means
1)it is a perfect square
2) It has no factors except 1, itself and its square root
3) The root must be prime (not split into other factors)
From this, we see that 11square (121), 13 square (169), etc r possible.
The sq. roots of the numbers are 11, 13, 17 , 19, 23, 29 and 31.
There are 7 such numbers out of 100 to 999
So, probability = 7 / 900
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22 Jun 2008 11:38:53 IST
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yup the answer is 7/900
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23 Jun 2008 19:39:49 IST
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