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Chris Lele

SAT Math Strategies: Ballparking (Estimation) and Plugging In

This is Not Your Average 10th Grade Math Class!

Remember that math teacher – the one who would drone on for hours, feverishly scribbling on the board, as though in a trance, his or her back turned to class? And remember the test that followed – a follow the step-by-step approach that put you in a similar zombie-like state?

Well, the good news is the SAT is nothing like that class. It is way better. In fact, it is fun. No I’m not joking – nor am I a ‘geek’ who scribbles formulas on my bathroom mirror every Friday night. That the SAT math is fun is something I hear from my students (who also do not have an affinity for graffiting their bedrooms with math formulas).

On the SAT, the math section is more of a logic game, a Sudoku puzzle with a countdown (you only have about 20 minutes on the SAT). And maybe you don’t think logical puzzles are necessarily fun, but compared to your average math class, they are a downright blast.

Okay, enough with the preamble. Let’s go through some important strategies (or tricks as many refer to them as). Call them strategies, call them tricks… the bottom-line, they will help you rock the SAT come test day. And, just as importantly, they make prepping for the SAT fun.


Strategy #1: Ball-parking (estimation)

If you are thinking of greasy hotdogs and the seven-inning stretch, you are in the wrong ballpark. In the  SAT world ballpark means guest-imating and is a quick trick to get a solution.

For instance, take a look at the following question:

Mike saved 20% on a shirt before taxes. If he paid $60 for the shirt, what was the original price of the shirt?

(A)  48

(B)  64.60

(C)  75

(D)  80

(E)  95


We know that Mike paid $60 for the shirt after the 20% discount. On what planet would the shirt have cost less before the discount? Obviously not Earth – so we can get rid of (A). (B) is also suspect because it is so close to 60. A 20% is pretty decent drop in price.

On the upper range, 95 is way too much. For if Mike is saving $35 on a shirt that costs less than a 100, he is obviously saving way more than 20%.

That leaves us with either (C) or (D). Ballparking won’t always help you get the answer, but it is a very effective way of eliminating most of the answers.

To figure out whether it is (C) or (D), I am going to show you another trick: plugging in.


Strategy #2: Plugging in

This question can be solved by a formula. Of course you have to know how to set up the formula (it’s 60 = 7/10 x). Yes, I already can sense some of you cringing. But that’s the beauty of the SAT – you don’t need no stinking formulas!

Think of it this way – you already have the answer. It’s one of the five below the question. If you’ve ball-parked – the way we did in the last problem – you can get the number of possible answer down to two. Let’s take a look again at Mike and his shirt.

Mike saved 20% on a shirt before taxes. If he paid $60 for the shirt, what was the original price of the shirt?

(C) 75

(D) 80


One of these is the answer. Which one? Let’s choose (C) and plug it back into the problem.  If the shirt was originally 75 dollars, and he saved 20%, let’s take 20% of 75. You can use your calculator, or you can use the shortcut.

What’s 10% of 75? 7.50. 20% is twice 10%. So twice 7.50 is 15. So what’s 15 dollars less than 75? 60. The answer.

If we do the same with answer (D), we get 20% off 80, which is 80 – 16 = 64. Mike did not pay 64 for the shirt so we know this is not the answer.

And just like that – no boring formulas – we were able to get the answer. See, I told you – SAT math can be fun. Just don’t carried away and start scribbling numbers on your bedroom wall!


About Chris Lele

Chris Lele is the GRE and SAT Curriculum Manager (and vocabulary wizard) at Magoosh Online Test Prep. In his time at Magoosh, he has inspired countless students across the globe, turning what is otherwise a daunting experience into an opportunity for learning, growth, and fun. Some of his students have even gone on to get near perfect scores. Chris is also very popular on the internet. His GRE channel on YouTube has over 8 million views.

You can read Chris's awesome blog posts on the Magoosh GRE blog and High School blog!

You can follow him on Twitter and Facebook!

2 Responses to “SAT Math Strategies: Ballparking (Estimation) and Plugging In”

  1. math therapy says:

    I believe most books give you 3 styles or strategies:

    1) Do raw algebra, not always the fastest but maybe to you it can be

    2) Plug in numbers for the variable solve for a target value from the answers

    3) Combine both techniques

    • Chris Lele Chris says:

      Yes, that is a pretty good summation. I think for many students they’ve only learned algebra, and are unsure of how to use the answer choices to arrive at the answer. For more difficult problems combining can sometimes work (of course checking your algebra with numbers is good for any level difficulty of problem, given one has time).

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