SAT Math Question of the Day

Q: If Set X = {4,5,6} and Set Y = {3,5,6,7}, then what is the union of Set X and Set Y?

1. {3,4,5,6,7}
2. {3,4}
3. {4,5}
4. {5,6}
5. {6,7}

UNANSWERED.

The correct answer is A.

A: {3,4,5,6,7} 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 X: 4,5,6.

Then we add in the elements from Set Y = {3,5,6,7} one at a time:
Add in the 3: union = 3,4,5,6
The 5 and 6 are already in the union, so we don't need to list them twice.
Add in the 7: union = 3,4,5,6,7
We finished adding all the elements from Set Y to Set X, so we're done. We have the union of Set X and Set Y.