3. Backsolving (ADVANCED)

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Backsolving involves inserting one of the five answer choices into the variables in the question. You obviously cannot use this on Data Sufficiency questions (where there are no answer choices).

When to Backsolve

• Want to to double check an answer? Backsolve your answer choice and see if it works. This is where Backsolving is most effective.
  
  
• You are completely stumped and you don't know what to do. Start plugging in answer choices and hope you get lucky! Even glancing at the answer choices may give you a concept of where the question is going and if you are on the right track. Note: try plow and playing with the numbers before backsolving.
  
  
• Sometimes you can use Backsolving to skip complicated algebra by substituting the numbers instead of trying to solve for the variables.
  

How to Backsolve:

1. Decide if the problem is too complicated to solve algebraically. Before Backsolving, try to Plow through the numbers and run some calculations. Don't jump to Backsolving too quickly.
   
   Note: sometimes a question will be so tricky that you won't even know how to backsolve the numbers into a question. In this situation, Backsolving is useless.
   
   
2. START AT (C). Insert the middle answer--the one that would be in the middle of potential answers if it were on a number line. The answer choices are usually arranged from lowest to highest value--answer choices A through E. You can adjust to pick (D)/(E) or (A)/(B) depending on whether you need a higher or lower number.
   
   
3. Eliminate the choices down to the one answer that works and choose.

	800score Tip: The reality is that multiple choice tests are fundamentally flawed in that you can Backsolve questions. The result is that the GMAT becomes a game of chess where Mr. GMAT knows that you can Backsolve. So questions are written with this in mind and designed not to be Backsolved effectively because they are so complicated. On the other hand, sometimes questions are designed where Mr. GMAT is testing your resourcefulness and expects you to have Backsolve in your bag of tricks.

Try Backsolving on this question:

When the positive integer Z is divided by 24, the remainder is 10. If Z is divided by 8 the remainder is 2. What is the value of Z?

a) 18
b) 34
c) 40
d) 49
e) 57

2. Don't Do That Math!

4. Plug In - Testing Numbers