SAT Math Question Serious Help!

Test Preparation SAT Preparation
1

<p>If X is the set of positive multiples of 2 and Y is the set of positive multiples of 3, the intersection of X and Y is:</p>

<p>A) the set of all positive even integers
B) the set of all positive real #'s
C) the set of positive multiples of 3
D) the set of positive multiples of 5
E) the set of positive multiples of 6</p>

<p>i can't believe i got this wrong. e is the correct answer, but why wouldn't C be correct??? I think i didn't know what "intersection" meant. well let's see.</p>

<p>Set X: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20
Set Y: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30</p>

<p>6, 12, and 18 are the intersections because both sets have them. So why wouldn't C work? 6, 12, and 18 are all positive multiples of 3 too. O_O</p>

2

<p>C contains elements that are not in both sets. For example, 9 (a multiple of 3) is in set Y, but not set X.</p>

3

<p>Yeah, you’re trying to find the intersection, not the union. You need to find the set that includes all the numbers contained in BOTH X and Y, but ONLY those numbers (no extras). Both X and Y could work, but they have extras. You need letter E for the right answer here.</p>

4

<p>The set for answer C is {3,6,9,12,…} but the set you found is {6,12,18,…}.</p>

<p>They are different.</p>

5

<p>The term “intersection” is not usually tested on the SAT–it only looks for your ability to use and manipulate sets. Is this from a prep book you’re using?</p>