SAT Math Question of the Day

Q: What is the union of Set A = {0,2,4,5,9} and Set B = {1,4,6,9}?

1. {0,1,2,4,5,6,9}
2. {0,2,4,6,9}
3. {0,2,5,6}
4. {4,6}
5. {4,9}

UNANSWERED.

The correct answer is A.

A: {0,1,2,4,5,6,9} is the correct answer.

To find the union of 2 sets, list all the elements from either set. So to get the union, we first include all the elements from Set A: 0,2,4,5,9.

Then we add in the elements from Set B = {1,4,6,9} one at a time:
Add in the 1: union = 0,1,2,4,5,9
The 4 is already in the union, so we don't need to list it twice.
Add in the 6: union = 0,1,2,4,5,6,9
The 9 is already in the union, so we don't need to list it twice.
We finished adding all the elements from Set B to Set A, so we're done. We have the union of Set A and Set B.