Question

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

Answer 1

The answer is 0.29

Explanation:

To select a set of numbers that sum of them can be divided by 3, we shouldn't pick 1 or 4. So total number of sets that can be selected from set A is:

`T=combination(7,3)=35`

Set of numbers set that sum of them can be divided by 3 is:

`t=combination(5,3)=10`

The probability is

`P=t/T=10/35=0.29`