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Kristin Fracchia

TuesdACT: ACT Math Practice – Estimation

In this episode of TuesdACT, we are talking about a really important strategy for the ACT Math that is going to help you instantly improve your score even when you don’t know how to do the problems. It’s that good. And it’s called estimation.

This video walks you through three incredibly helpful ways (with examples!) that you can use estimation to your advantage on the ACT.

1. Eliminate answers that are unrealistic.

It’s so important that you take advantage of the fact that this test is multiple choice. The answer is right there in front you of, and, for whatever reason, the ACT often includes some incredibly unrealistic answers amongst your choices—values that are way too high or too low. However, they might be numbers that you would obtain if you messed up your calculations. And that’s why it’s so important that you break the habit of the “school way” of doing problems and use some common sense. If you determine that a $85 dollar sweater on sale for 20% off would cost $17….well, that wouldn’t make sense. So get in the habit of eliminating too small or too large answer choices right off the bat.

2. Simplify equations by approximating values.

When answer choices are very much spread out, you can often get the answer more quickly by approximating easier values for the numbers than by reaching for your calculator. (See the video for an example!)

3. Estimating on geometry problems.

For the most part, you can assume diagrams are drawn roughly to scale on the ACT. This means there are few tricks you can employ on the paper test to get an answer even when you don’t know how to do a problem. For example, you can turn the side of your answer sheet into a ruler by making light pencil marks to show the known lengths of lines in a diagram and then put this “ruler” up against an unknown line in the diagram to estimate its length. You can use the corner of your answer sheet as a handy right angle to help estimate the size of an unknown angle. Even just eyeballing a diagram can often help you eliminate unrealistic answer choices.

Even if you don’t know how to do a problem and need to take a guess, in many cases on the ACT, you can greatly improve your odds of guessing correctly through estimation, so don’t just assume* you have to just blindly guess!

*Magoosh does not claim responsibility for the terribleness of this pun.


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About Kristin Fracchia

Kristin makes sure Magoosh's sites are full of awesome, free resources that can be found by students prepping for standardized tests. With a PhD from UC Irvine and degrees in Education and English, she’s been working in education since 2004 and has helped students prepare for standardized tests, as well as college and graduate school admissions, since 2007. She enjoys the agony and bliss of train running, backpacking, hot yoga, and esoteric knowledge.

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