Sets
Sets are discrete groups of items. For example, the number
of people who received a B in Mr. Japlonski’s chemistry class can
be considered a set. A set contains only those things that can fit
its definitions. If a student got an A in Mr. Japlonski’s class,
he cannot be in the set of students who got Bs. If you have a set
that is defined as
(1, 2,
), then the only
things that can be in that set are
(1, 2,
).
Really, on the SAT, sets don’t get much more complicated than that.
The One Exception
That is, set questions don’t get more complicated except
for one specific type of question. In this question, the SAT will
describe two sets and a few people who fit into both sets. Then
it will ask how many total people are in the two sets. For example:
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Of
the lions at the zoo, 13 eat zebra meat, 11 eat giraffe meat, and
7 eat both. How many total lions are there in the zoo? |
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When you read it, this question just feels like
it’s going to be very hard. A lot of students will therefore not
even try to answer it. So what does that mean to you? It’s a chance
for you to gain points in comparison to other students. Luckily,
this type of question is actually quite simple to answer, as long
as you know and use the following formula:
Total = number in set 1 + number in set 2
– number common to set 1 and 2
To answer the question about the lions, write:
Total lions = 13 zebra eaters + 11 giraffe
eaters – 7 eaters of both Total lions = 17
Once you know the formula, all you have to do is figure
out which numbers in the word problem define set 1,
which define set 2, and which define the overlap set.
After that, you just have to plug in the numbers and do some simple
addition and subtraction.
