
Originally Posted by
crazy_gal108
3. Six students are asked to secretly choose a number from 1 to 15. Determine the probability that at least two students choose the same number to the nearest thousandth.
Since we are talking 'bout thousands only the first three digits are important. Thus, all the numbers are,
Code:
1.000
1.001
1.002
........
14.998
14.999
15.000
To make the problem easier, let us do the opposite statement. Meaning, the probability that 6 students do not choose the same number and then from that subtract one.
There are a total of 14,001 numbers.
STUDENT1)Can chose any one thus probability is 1.
STUDENT2)Can chose any number except that of student1, thus the probability is 
STUDENT3)Can chose any number except that of student1 and student2 thus the probability is 
STUDENT4)Probability is 
STUDENT5)Probability is 
STUDENT6)Probability is 
Thus, the probability that they DO is,

Evaluating we find that,
0.0010709185167321222566663866769298
Is the probability thus,
a little more than 1%