problem 258 mathcounts

Mathematics
Tutor: None Selected Time limit: 1 Day

6 integers 1,3,5,7,9,11 form an arithmetic sequence.If 3 of the integers are selected randomly without replacement,what is the probability that they form an arithmetic sequence in the order they are selected?Express your answer as a common fraction.

Oct 19th, 2014

1,3,5,7,9,11

could be looked at as drawing numbers out a hat. The probability of picking one number would be: 1/6

The probability of 3 integers being selected in order would be: (1/6) * (1/5) * (1/4)

The denominator is decreasing by one because you are taking a number out of the whole.

If you multiply the fraction out you would get: 1/120


Oct 19th, 2014

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