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Backsolving vs plugging in answer choices

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Backsolving vs plugging in answer choices

by GeauxSwish » Sat Feb 04, 2017 2:51 pm
Howdy! I'm a bit confused of the difference between back solving and plugging in answer choices. I understand certain types of problems are better for certain strategies. And could someone provide an example?

I'm also trying to understand if that means certain strategy are good for questions that deal with certain concepts (ie remainder questions) OR if they are best used for certain question fromats(ie solving for a variable, variable in answer choice, etc).
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by [email protected] » Sun Feb 05, 2017 10:45 am
Hi GeauxSwish,

Most of the questions that you'll face on the Official GMAT are designed so that they can be solved using more than once approach. In that way, the Test actually 'rewards' strong critical thinkers - those same thinkers will be more likely to find the 'fast way' to get to the correct answer and can avoid long, difficult, overly-technical approaches. By extension, those same thinkers are less likely to get 'stuck' and less likely to deal with pacing issues that hinder how high many Test Takers can score.

Since the GMAT is a constant, predictable Exam, you can learn to take advantage of the patterns and design 'elements' that GMAT question writers typically use. Knowledge of those patterns isn't enough though - you still have to train to spot all of those patterns AND physically practice working through all of the 'steps' needed to get to the correct answer. The specific Tactic that you've referenced goes by different names (depending on who is teaching you): TESTing THE ANSWERS, Backsolving, Plugging in answers, etc.

Here's an example of a question that can be solved by TESTing THE ANSWERS:

https://www.beatthegmat.com/rate-filling ... 76477.html

Ultimately, the 'best' approach for any given prompt will depend heavily on two things: the 'design' of the question and your knowledge/ability with the various approaches. Thankfully, you CAN train to learn all of the necessary skills to score at a high level - you just have to make sure that you're using the proper study materials and that you're properly practicing.

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by GeauxSwish » Sun Feb 05, 2017 7:35 pm
[email protected] wrote:Hi GeauxSwish,

Most of the questions that you'll face on the Official GMAT are designed so that they can be solved using more than once approach. In that way, the Test actually 'rewards' strong critical thinkers - those same thinkers will be more likely to find the 'fast way' to get to the correct answer and can avoid long, difficult, overly-technical approaches. By extension, those same thinkers are less likely to get 'stuck' and less likely to deal with pacing issues that hinder how high many Test Takers can score.

Since the GMAT is a constant, predictable Exam, you can learn to take advantage of the patterns and design 'elements' that GMAT question writers typically use. Knowledge of those patterns isn't enough though - you still have to train to spot all of those patterns AND physically practice working through all of the 'steps' needed to get to the correct answer. The specific Tactic that you've referenced goes by different names (depending on who is teaching you): TESTing THE ANSWERS, Backsolving, Plugging in answers, etc.

Here's an example of a question that can be solved by TESTing THE ANSWERS:

https://www.beatthegmat.com/rate-filling ... 76477.html

Ultimately, the 'best' approach for any given prompt will depend heavily on two things: the 'design' of the question and your knowledge/ability with the various approaches. Thankfully, you CAN train to learn all of the necessary skills to score at a high level - you just have to make sure that you're using the proper study materials and that you're properly practicing.

GMAT assassins aren't born, they're made,
Rich
Thanks. I get that, but you didn't really answer the question. That might be on me for not phrasing it properly.
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by [email protected] » Sun Feb 05, 2017 8:19 pm
Hi GeauxSwish,

Could you go into more detail about what you're specifically interested in?

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by GeauxSwish » Sun Feb 05, 2017 10:04 pm
[email protected] wrote:Hi GeauxSwish,

Could you go into more detail about what you're specifically interested in?

GMAT assassins aren't born, they're made,
Rich
Sure. Backtracking a bit, your last post made total sense just wasn't exactly what I was looking for. Back on track

Main Question
What is the difference between when someone says "Plug in answer choices" versus "backsolve"? Do I take the answer choices and use those values? If I do that is that backsolving or plugging in? I know ultimately I am plugging a number in at some point, but where are those number coming from?


AND then, part two, once I then figure out the difference between "backsolving" and "plugging in answer choices" I understand that each kind are better for certain situations. HOWEVER, when they say that certain strategies apply to certain question types, do they mean types as in certain types of as in skills tested OR certain types of problems as in certain formats of the way the problem and answer choices are presented. Though I think you answered this question from your first post.
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by [email protected] » Mon Feb 06, 2017 9:55 am
Hi GeauxSwish,

As I mentioned in my first post, "plugging in the answers" and "backsolving" are the SAME thing - in specific situations, you can use the answer choices 'against' the prompt and do the necessary 'math work' to find the answer that "fits" the information that the prompt gives you. Once you're comfortable with this approach, it will be significantly faster than the algebraic approach that will also be possible on those questions. This Tactic isn't an option all that often though in the Quant section; you'll likely be able to use it 2-3 times on Test Day though (and there's a reasonable chance that you will be able to use it in the IR section too).

Some Test Takers refer to TESTing VALUES as "plugging in", but that is a bit different from backsolving. In that situation, you get to choose any value (or values) that you like, so you have to consider which value(s) would make the work easy to deal with. TESTing VALUES can be used on over half of the Quant questions that you face - AND it's a great way to prove that a math pattern exists if you're ever stuck on a question.

While certain Quant subjects tend to be more susceptible to certain Tactics (for example, Number Property questions are almost always beatable by TESTing VALUES), you will generally need to consider the 'design'/style/format of each prompt to determine which approaches are applicable (and often the answer choices provide a clue as to how best to proceed).

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by ceilidh.erickson » Wed Feb 15, 2017 11:31 am
GeauxSwish wrote:Howdy! I'm a bit confused of the difference between back solving and plugging in answer choices. I understand certain types of problems are better for certain strategies. And could someone provide an example?

I'm also trying to understand if that means certain strategy are good for questions that deal with certain concepts (ie remainder questions) OR if they are best used for certain question fromats(ie solving for a variable, variable in answer choice, etc).
"Backsolving," "working backwards," and "plugging in the answer choices" are the exact same strategy! They're just two different names for the same principle. I've outlined exactly how and when to use this strategy in this article:

https://www.manhattanprep.com/gmat/blog ... m-solving/
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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by Matt@VeritasPrep » Thu May 11, 2017 8:11 pm
It is worth distinguishing plugging in the answer choices from simply plugging in. The former means taking the answers and trying them, the latter means using your own numbers to solve a word problem with variables in the answers.

I do think that backsolving entails more than just plugging in the answers: it can mean eyeballing the answers, seeing some pattern or detail to them, and using that to spark an approach to the problem. (For instance, they're all prime, which means there's something about this problem that might demand prime numbers.) That's not too important a distinction, however.
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