Data Sufficiency
WHAT IS DATA SUFFICIENCY?
Every Data Sufficiency problem consists of a question followed by two
statements. You have to decide NOT WHAT THE ANSWER IS, BUT WHETHER THE QUESTION
CAN BE ANSWERED based on the information given in the two statements. Let us
take a very simple example;
What is x?
A. x + y = 17
B. 4x + 4 = 18
As in any other question in CAT, there are four alternative answer choices.
- if the question can be answered by one of the statements
alone, but cannot be answered by using the other statement
alone.
- if the question can be answered by using either statement
alone.
- if the question can be answered by using both the statements
together, but cannot be answered by using either statement
alone.
- if the question cannot be answered even by using both
statements together.
Here�s how to crack it
The best way to answer Data Sufficiency problems is to look at one statement at
a time. So cover statement (B) with your hand.
Based on statement A, x + y = 17 can we answer the question �What is x?�
No way. If x + y = 17, there are many possible values of x: If y equals 2, then
x could equal 15. On the other hand, if y equals 13, then x could equal 4.
Statement A is not sufficient to give us a single value for x.
Now forget you ever saw statement A. Cover it up with your finger and look only
at statement B � 4x + 4 = 18. Based on statement B alone, can we find a single
value for x?
Yes. Using algebraic manipulation, we can do the following:
4x + 4 = 18
4x = 14
So, x = 3.5
Note that the question isn�t asking us what x equals. The question asks
only whether the information provided is sufficient to find out what x equals.
In this case it is; statement B gives us enough information to answer the
question �What is x?� Since B is sufficient and A is not, the answer to this
question is:
- if the question can be answered by one of the statements alone, but
cannot be answered by using the other statement alone.
Note
CAT has been using different versions of what the four answer choices stand for.
Therefore, it is imperative that you read the instructions given before the Data
Sufficiency question in every paper and then answer them. For intance, in CAT
2003 re-test, the choices were different from what are given in the above
sample. Many students who did not read the instructions carefully answered these
questions wrong despite knowing how to solve them.
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