Set A: {1, 3, 4, 6, 9, 12, 15}

If three numbers are randomly selected from set A without replacement, what is the probability that the sum of the three numbers is divisible by 3?

A. 3/14

B. 2/7

C. 9/14

D. 5/7

E. 11/14

The sum of any three number from set B={3,6,12,15} would be divisible by 3. with combination method we can find how many ways we can select 3 numbers from set B. 5C3 = 10 so the probability would be

10/72nd method is of probability: The easy would be not selecting 1 and 4 from the set.

so P(not 1 and not 4) = P (not 1) * P(not4) => (1-1/7) * (1-1/6) =>

5/7Both Answers are wrong !!

where i'm going wrong.

Thanks

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