Going to the Answer Choices
Going to the Answer Choices
We’ve told you not to look at the answers. Now we’re going to amend that advice: you shouldn’t look at the answers unless you’ve taken the time to try to understand a question, and you’ve come to the conclusion that going to the answers and using them to try to answer the question is your best strategy. There are two reasons why you might come to this decision:
  1. You think plugging in the answer choices is the best tactic for approaching the question.
  2. You’re not sure exactly how to answer the question, and you think you can either eliminate all the wrong answers—or at least some of them—by working with the answer choices.
Whatever your reason, make sure you approach the answer choices critically and strategically. Don’t let them influence you. Try to see how you can use them.
Take the following example:
A classroom contains 31 chairs, some of which have arms and some of which do not. If the room contains 5 more armchairs than chairs without arms, how many armchairs does it contain?
A. 10
B. 13
C. 16
D. 18
E. 21
Given this question, you could build the equations:
Then, since y = x5 you can make the equation:
There are 18 armchairs in the classroom.
This approach of building and working out the equations will produce the right answer, but it takes a long time! What if you strategically plugged in the answer choices instead? Since the numbers ascend in value, let’s choose the one in the middle: C, 16. This is a smart strategic move because if we plug in 16 and discover that it is too small a number to satisfy the equation, we can eliminate A and B along with C. Alternatively, if 16 is too big, we can eliminate D and E along with C.
So our strategy is in place. Now let’s work it out. If you have 16 armchairs, then you would have 11 normal chairs and the room would contain 27 total chairs. We needed the total numbers of chairs to equal 31, so clearly C is not the right answer. But because the total number of chairs was too few, you can also eliminate A and B, the answer choices with smaller numbers of armchairs. If you then plug in D, 18, you have 13 normal chairs and 31 total chairs. There’s your answer.
In this instance, plugging in the answers takes less time and, in general, just seems easier. Notice that the last sentence began with the words “in this instance.” Working backward and plugging in is not always the best method. For some questions, it won’t be possible to work backward at all. For the test, you will need to develop a sense of when working backward can most help you. A good rule of thumb for deciding whether to work backward is:
  • Work backward when the question describes an equation of some sort, and the answer choices are all simple numbers.
If the answer choices contain variables, working backward will often be quite difficult—more difficult than working out the problem would be. If the answer choices are complicated, with hard fractions or radicals, plugging in might prove so complex that it’s a waste of time.
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