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3 Math Facts All Kids Need to Know (But Many Do Not)

Graffiti mathWith school back in session, I find myself reteaching and refreshing students on a very familiar (to me, anyway) list of math concepts. By now I think of them as The Usual Suspects.

I hope parents will find it reassuring to know that it’s not just their kid who can’t seem to retain certain math facts. Students from middle school all the way up through 12th grade have trouble making some fundamental math ideas stick.

But parents also need to to realize that it’s these “little details” which trip kids up in big ways and prevent them from being great math students. Indeed, most calculus students who drop out, do so not because they find the calculus itself hard, but because their math foundations are weak.

Here are three concepts that bear repeating to your middle school or high school child. Some parents are keeping flash cards in the car for flipping en route to school; a great idea! (Meanwhile, I’ll keep collecting more Usual Suspects and publishing them throughout the school year).


1. What does product mean?

Product is the answer you get when you multiply. 

Ex: 6 is the product of 2 and 3.(Many students confuse product with sum; the sum is what you get when you add. The sum of 2 and 3 is 5).

2. How do you write a subtraction expression, such as six less than x?

Be careful when you write subtraction expressions, because often you need to write them “backwards.”

Ex: Six less than x is not 6 – x, it’s x – 6.

It may help to first think about a purely numerical example: How would you write 2 less than 10?  You would write 10 – 2. (The answer would be 8).

3. When you add or subtract fractions, you first need to have common denominators.

I often catch 12th graders still writing 1/2 + 1/3 = 2/5 (Gak!!)

Unfortunately, you can’t just add the numerators and add the denominators.

Instead, you first need to change 1/2 into 3/6, and 1/3 into 2/6.

Then, how many sixths do you have? 3/6 + 2/6 = 5/6.

So, 1/2 + 1/3 = 5/6.


If anyone in your family needs a more thorough refresher on common denominators, try this very helpful Khan Academy video:

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3 Math Facts All Kids Need to Know (But Many Do Not)

Leigh Pretnar Cousins, MS

Leigh Pretnar Cousins, MS is an educator, counselor, writer and speaker. She's been a tutor, test prep coach and home school teacher for over thirty years. Click HERE to visit Leigh's website and to subscribe to her newsletter, "Learning Something New."

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APA Reference
Cousins, L. (2015). 3 Math Facts All Kids Need to Know (But Many Do Not). Psych Central. Retrieved on November 28, 2020, from


Last updated: 13 Sep 2015
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