Using Smart number is a terrible strategy

Question

Hi all,

I recently started MGMAT Quant books. In the initial chapters I am reading about this strategy which I don't know whether other GMAT courses suggest or not: 
Smart numbers: this method suggests that instead of using abstract x , you should take a number and do the calculations on it and then find the correct answers by plugging the answer in every option. I was like "what?" Correct me if I am wrong, isn't it much easier to work with X and when you don't need to plug anything (which I believe super time consuming) . I really want to hear your opinions on it? This method really irritated me because of the education background I guess . I am so comfortable with working X and Y etc. so it is no issue for me. But if US school system uses this method well good luck to them

kiran120680 · Answer

Plug in the number some time lead to a trap. If not plugged in all the numbers(integers, Rational, Natural, negative..). So try to avoid plug in numbers maximum.

akela · Answer

Hi Elnur , The GMAT math section demands flexibility, and having alternative approach to solve a problem can help improve the overall score. Check these two articles to learn more: https://magoosh.com/gmat/2013/how-to-pl ... questions/ https://magoosh.com/gmat/2013/backsolving-on-gmat-math/ Hope this helps!

pvs29 · Answer

I think in this regard, Math Revolution is a great source. It has strategies, but these aren't completely fixed, per se. You should look at the question and identify.

Sometimes it may be simpler to solve the question algebraically, whereas the number input method would take a lot of unnecessary time!

Maxximus · Answer

Hello @Ellnur, Interesting question. First thing first- none of these smart methods work for all; hence, if a suggested shortcut irritates you (as you said), skip it and use a conventional way for solving problems. For example, for several mixtures questions, "Alligation" is a great way of solving questions but many candidates find it confusing and hence, are advised to simply stick to the conventional (weighted average) way. Regarding your exact query here, it does make sense to assume values in certain type of questions- especially where the desired answer is supposed to be in percentage or ratio. For example, here is an example of using 100 as base for solving questions where % change in a value is asked- https://www.youtube.com/watch?v=0SUmg3ePTyg However, once again, to use this method is a matter of choice and not compulsion. Once again, when a shortcut sounds more complex than a conventional solution, the shortcut is not for you

All the very best! Experts' Global team

IanStewart · Answer

I've long had the impression that many prep companies have a philosophy that "GMAT test takers can't do math". In my experience, that is untrue - my students have always been very capable at math, provided they learn it the right way. But many prep companies teach "strategies" (like 'number picking' or 'backsolving') to help test takers avoid doing algebra. There are a few problems with those strategies:

- they are often much slower than 'doing the math'
- when they work, they are less reliable than doing the math (for example, in 'must be true' questions, you often can't be completely sure you have proven that something is always true, or is only true for the numbers you picked)
- they tend not to work at all on higher level questions

There are, however, some important exceptions - in certain question types, picking numbers is both 100% reliable, and much faster than using algebraic approaches. So part of getting good at GMAT math is learning to recognize when to use which strategy. But if you are using these company strategies as your default approach to all questions, you're truly capping your score, since you simply won't be able to answer the hardest questions, and if you're comfortable with either conceptual or algebraic approaches to problems, you have a big advantage if you're aiming for a top score.

I'd add though that these company strategies can be very useful for a test taker currently at a below average level who is merely aiming for an average score. Those strategies can often successfully be applied to easier questions, and if someone genuinely does have difficulties with algebra, those strategies can help. But it doesn't sound like you're in that situation at all.

Abhi077 · Answer

Plugging in smart numbers doesn't work out every-time and for everyone. to each it's own after all. Certainly with more practice, this strategy becomes comfortable..and you have to be really smart whilst picking smart numbers..glancing at answer choices helps too. imo you should do all the trial and errors and stick to the one which works best for you.

ccooley · Answer

The US school system doesn't (extensively) use this method, which is one reason we teach it! I went to school in the US and I never learned it until I started working in the standardized testing industry. It's a new skill for a lot of people, and it's unfamiliar. There's also definitely a learning curve. When somebody learns about using smart numbers for the first time, they'll almost certainly be slower and less accurate than they are with algebra. But that's why you learn about it well in advance of taking the test - so you have time to practice and master it. Because there are definitely problems on the GMAT for which smart numbers will be faster and more accurate for most people. (I've scored 51 on Quant and I use it at some point during every GMAT I take.) I think there are two good reasons to bother learning it. One, smart numbers can serve as a sort of "safety net" - knowing how to use the strategy can help you double-check your work on relatively straightforward problems. This is particularly true (at least for me) when the problem involves unit conversions. Here's an example of the type of problem where smart numbers might be "safer": cheese-that-costs-c-cents-per-ounce-costs-how-many-dollars-per-pound-273757.html If I saw this problem on my GMAT, I'd probably solve it algebraically, but then I'd double check with smart numbers to be sure that I hadn't mixed up pounds and ounces, gotten any of my fractions upside down, etc. It's a relatively easy problem, but the risk of falling into a trap is high, and for most of us, we have significantly better intuitions about numbers than we do about variables. "$14" might look right or wrong, while "7x - 4" doesn't really look right or look wrong necessarily. Two, using smart numbers is sometimes easier , even if it might also be slower than using variables. For instance, I tend to use smart numbers for problems that heavily use percents, especially percent change, because it's easier for me to do math on paper with integers than with decimals ("85" is easier than "0.85x"). That said, if you already find the variable approach to be more than easy enough, this point won't matter to you! At the end of the day, we teach the strategies we teach because we want people to get more (and harder) problems right. If you learn something thoroughly and it's not helping you get any more right answers, then toss it! But I'd also recommend not tossing anything until you're comfortable using it, just because of the learning curve factor...

Using Smart number is a terrible strategy

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