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The Zinc Blog

Put Down the Calculator for a Minute

Why We Teach Mental Math

Can you multiply simple two-digit numbers, like 39 times 24, in your head?

Hang on a minute, you may be asking. Why would I do that when I can just pick up my calculator?

That’s true, and there are times when a calculator may be a better option. But we see too many students who suffer from a debilitating calculator dependency. Building up your facility with mental math so you’re not overwhelmed by problems like the one above (it’s not that hard—see the explanation below1) gives you a better handle on the behavior of numbers. Ultimately, it’ll make you faster and more accurate on the tests. 

Many students have learned math by memorizing rules without a deeper understanding of what they mean. The result? A majority of test-takers will be confronted with very simple problems and react by doing something that doesn’t make the best sense. We call this approach automath, and we’re on a mission to eradicate it! 

Here’s an example:

x + y = 17

x * y = 72

How would you go about finding x and y? Most students will set up several lines of algebra on the page and diligently work their way through the way they were taught in school.

But perhaps instead of rushing into automath, you simply thought about the problem for a minute. You may have been able to try a few options and see that only two numbers fit in both equations (the answer to this one is also at the end of the page2). In this case, breaking the habit of automath allowed us to see a much faster and easier way to arrive at the solution.

Practicing mental math is a big part of Zinc tutoring and teaching. It helps students think more flexibly as they notice the patterns in how numbers fit together. Processes like multiplication, which most of us crammed in through painful memorization, start to become less abstract, more real. In a very short time, the old anxieties about math are knocked out of the way as students start to pick up on the actual pleasure of problem-solving. After all, math is fun when you know what’s going on.

Yes, mental math is hard. It’s a challenge, but we guarantee it’s a winnable one. With practice, anybody can get much better at it in just a couple of weeks. It works your brain and gets you comfortable with struggling and solving problems, and when it comes to your ability to function on a test, mental math gives you a much higher technical baseline as well as an essential sense of competence and confidence. As a recent student in our Advanced Math Foundations class reflected, “I’ve learned that having mental math skills perfected can really help you overall.”

Ready to up your math game? Try this 30-second arithmetic challenge, a favorite among Zinc tutors and teachers. You can also give us a call or send us an email to learn more about our upcoming Advanced Math Foundations classes, one-on-one tutoring, and SAT/ACT Boot Camps.


1 To solve 39 times 24, multiply 40 times 20 (which is 800) plus 40 times 4 (which is 160). Add those together to get 960 and then take away 24, since you’re only asked for 39 of them. The answer is 936.

2 The only two numbers that fit both equations are 8 and 9.

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