Do you collect stamps, bottle caps, or tissues sneezed in by famous people? If so, your collection is a set. The PSAT/NMSQT doesn’t care about the stuff you display on your wall (though a mental health professional may want to know more about your interest in tissues). The exam evaluates how well you deal with mathematical sets. No worries — all you need to remember are a few facts:

• The elements of a set are enclosed by brackets:{–2, –1, 0, 1, 4, 6, 7}

• If the set continues, you see three dots after the last element: {2, 4, 6, 8 . . .}

• A set with nothing in it — not even one element — is called an empty set and may be represented by brackets with nothing between them: { }. An empty set is usually represented by a crossed-out zero:

• To find the union of two sets, put them together and then cross out any elements that show up more than once. For example, the union of {5, 5.5, 6, 6.5} and {6, 7, 8} is {5, 5.5, 6, 6.5, 7, 8}.

• To find the intersection of two sets, see which elements they have in common. In the preceding bullet, the intersection of the two sets is {6}, because that’s the only common element. If two sets have no common elements, the intersection is an empty set.

If all the PSAT/NMSQT asked you to do was to look at lists of numbers, set questions would be no-brainers. However, they favor questions like “what is the intersection of the set of two-digit prime numbers less than 19 and the set of odd numbers from 11 to 35?” The answer, by the way, is {11, 13, 17}.

Try these two set questions:

1. How many elements are the intersection of the sets {E, G, I, R} and {I, K, R, S, T}?

(A)    1
(B)    2
(C)    4
(D)    5
(E)    7
2. Set A = {1, 2, 3, 4, 5}, set B = {2, 4, 6, 8}, and set C = {2, 3, 5, 7}. Which element is not in the union of sets A and C?

(A)    2
(B)    3
(C)    4
(D)    5
(E)    6