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Wednesday
Mar282012

How effective is plugging numbers when solving GMAT problems?

The video below illustrates how to apply the approach of plugging in numbers to solve GMAT problems, and the limitations of this approach. I also compare the plug in approach to the direct approach. Here is the summary of the key points:

Advantages of Plug in approach:

  • It is easy to implement and the easier algebraic/word problems can often be solved by using simple numbers. 
  • Sidesteps the necessary algebra. This is one of the main reasons why a lot of test prep books recommend plugging numbers because many students are weak in algebraic procedures.

Drawbacks of Plug in approach:

  • The choice of numbers to pick is important, because that can influence the amount and complexity of the ensuing numerical work.
  • In case of difficult problems, the amount of numerical work and the likelihood of making mistakes increases.
  • To be absolutely certain of the correct choice, one needs to test all of the answer choices.
  • In case of very difficult problems, the amount of work may exceed the amount of time it may take to approach the problem directly. 

Advantages of direct algebraic approach:

  • Direct and fast, and no need to spend time in thinking about appropriate choice of numbers. 
  • In case of difficult problems, the most efficient and fastest method is often the direct algebraic approach.
  • In case of data sufficiency problems that require one to translate a particular word statement to an algebraic expression and subsequent simplification, the ability to solve the entire question might rest on being comfortable with the direct algebraic approach.
  • The harder problems often require a strong grasp of algebraic procedures and this skill is necessary to obtain a high score on the GMAT.

Drawbacks of direct algebraic approach:

  • Difficult to implement if one is not comfortable with manipulating algebraic expressions and simplifying them with accuracy.

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