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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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Moderation Team
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