Data sufficiency

Introduction

Data sufficiency questions primary concern is to test how well you can reason quantitatively. This differs widely from quantitative section, Quant section tests your ability of manipulating numbers whereas data sufficiency tests your reasoning ability. What you shouldnt be doing while solving data sufficiency questions is wasting lot of time in manipulating numbers.If you are spending enormous time in solving DS problems then you are going wrong somewhere.
Concepts necessary to solve DS Quest.

The data sufficiency questions covers maths and algebra concepts that are taught in High schools and colleges. In addition to basic arithmetic, you can expect questions testing your knowledge of averages, fractions, decimals, algebra, factoring, and basic principles of geometry such as triangles, circles, and how to determine the areas and volumes of simple geometric shapes.
The Answer Choices

The answer choices are summarized below as you will see them on the CAT exam. Its better to memorise this before taking CAT so that you can devote this time in other sections.

1. Statement 1 alone is sufficient but statement 2 alone is not sufficient to answer the question asked.
2. Statement 2 alone is sufficient but statement 1 alone is not sufficient to answer the question asked.
3. Both statements 1 and 2 together are sufficient to answer the question but neither statement is sufficient alone.
4. Each statement alone is sufficient to answer the question.
5. Statements 1 and 2 are not sufficient to answer the question asked and additional data is needed to answer the statements.

Use Process of Elimination

If statement 1 is insufficient, then choices A and D can immediately be eliminated.

Similarly, if statement 2 is insufficient, then choices B and D can immediately be eliminated.

If either statement 1 or 2 is sufficient on its own, then choices C and E can be eliminated.

Data Sufficiency Tips and Strategies

1. Use only the information given in the questions. The CAT seeks to measure your ability to distinguish facts from careless assumptions. Do not rely on a visual assessment of a diagram accompanying a geometry question to determine angle sizes, parallel lines, etc. In addition, do not carry any information over from one question to the next. Each question in the data sufficiency section of the CAT stands on its own. You can count on seeing at least a few questions where a wrong answer choice tries to capitalize on this common fallacy.

2. Do not get bogged down with complicated or lengthy calculations.

3. Use process of elimination.

4. Be on the lookout for statements that tell you the same thing in different words.

When the 2 statements convey the same exact information, you will know, through process of elimination, that the correct answer choice is either D or E. A favorite ploy of CAT testers is to mix ratios and percentages. Here is an example where Statement 2 simply states backwards the exact same information provided by Statement 1.

1. x is 50% of y
2. the ratio of y:x is 2:1

5. Make real-world assumptions where necessary.

6. Practice, practice, practice.

Remember Nothing is Impossible because the word itself says I am Possible.