# When you say "math facts" what do you mean?

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I keep seeing posts about helping children memorize their "math facts" and I have no idea what you're talking about. It seems to go beyond times tables. What are these mysterious facts?

It is just knowing things like 6+2=8 down cold so you don't have to do the calculation?

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It is just knowing things like 6+2=8 down cold so you don't have to do the calculation?

YEP! :)

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All four operations. Facts through the twelves or fifteens.

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Addition and subtraction up through 20

Multiplication and division up through either 10 x 10 or 12 x 12 (depends on the particular curriculum you're using)

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This brings up a question I've been pondering- when I was a kid, we were expected to memorize the multiplication facts through 12x12, but many people today only do 10x10. And of course it would be possible to go higher.

What do you find works best?

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We only do addition up to 10, and multiplication up to 10. But we use a base 10 math so for any higher amount you just shift the number to suite you.

Heather

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As part of their pre-algebra curriculum, my older kids were required to know the decimal and percentage equivalents for common fractions (and vice versa)-----not just the thirds and quarters and fifths but the sixths, sevenths, eighths, and ninths. Automatic conversion has been such a help for them in advanced maths (they are now taking AP Stats and Alg2/Trig).

I am requiring dd10 to learn the same. She's not doing drill-type work but just using those decimals/percentages/fractions in her daily work, mainly word problems 'cause I'm being mean :D

Concerning times tables, I feel that everyone should know up to 15x15 :)

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Concerning times tables, I feel that everyone should know up to 15x15 :)

But why? Why 15 instead of 13 or 17? (examples chosen because knowing the primes could be of particular value.) 15, in particular, seems exceptionally useless, since computing the answer is so trivial, and detecting any multiple of five so simple.

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But why? Why 15 instead of 13 or 17? (examples chosen because knowing the primes could be of particular value.) 15, in particular, seems exceptionally useless, since computing the answer is so trivial, and detecting any multiple of five so simple.

Yep!

Besides with anything above 10 it is just as fast to break into two multiplication problems and add them and much less painful because it requires no memorization. For example:

14x9

10x9=90+4x9=36

90+36=126

Heather

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Addition (and subtraction) to 10+10 and the ability to use those to add and subtract bigger numbers.

Multiplication (and division) to 10x10... and the ability to use those to multiply and divide bigger numbers.

Then: Perfect squares to 20x20 and cubes to 10x10x10, fractions to decimals and percents for 1/2, thirds, quarters, fifths, and tenths.

There are some more things he had to remember after we hit algebra (square of the sums, etc.) but for straight arithmetic facts that's what I want.

ETA: Oops -forgot one!! powers of 2 up to 2^10=1024. :)

Edited by KAR120C
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addition and subtaction to to 9+9

skip counting through 10's up and down

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Subtraction to 20-10

Multiplication to 12x12

Division to 144/12

Over time they get familiar with some of the others as well.

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The 12's tables is useful because so many things come in dozens. Anything higher than that just seems arbitrary to me. In real life, when am I going to need to know the answer to 14 x 13 instantaneously?

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OK, so to follow-up, do most people drill and memorize these facts in isolation? I mean, the times tables I get, and I think up to 12 x 12 should be absolutely down cold. But, while I have personally "memorized" addition facts, I can't remember them ever being consciously memorized. I feel like I just added 5+2 enough times that eventually I just knew it was 7.

I mean, just from using RightStart, with its emphasis on not counting, my DD knows everything up to 5+5 without having to think about it. It seems to me the rest of them will come the same way, just practicing enough times so it's second nature. Am I naive? Or is that just another way to drill?

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That's the way it worked for most of my kids. For one kid, the times tables needed a little more focused work the summer before 5th grade. We play a lot of games, and that helps a ton. Plus I let them use manipulatives whenever they want.

I personally find that the knowledge is richer and more useful when it comes from tackling the problems from all kinds of angles. For example, reducing fractions really solidifies multiplication and division facts, because you have to be able to do them both ways: 7x4=28, but also recognizing that 28 can be broken into 7x4. In the case of something like 24, it helps you see how it can be factored in a whole bunch of ways - there's a 6 in there, or an 8, or a 3, and so on. (I don't teach reducing fractions by trying to find the largest factor; rather we find any factor and keep reducing until it's in simplest form. As they get more proficient, they start to choose larger numbers, so as to reduce the amount of work, a powerful motivation!)

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Addition (and subtraction) to 10+10 and the ability to use those to add and subtract bigger numbers.

Multiplication (and division) to 10x10... and the ability to use those to multiply and divide bigger numbers.

Then: Perfect squares to 20x20 and cubes to 10x10x10, fractions to decimals and percents for 1/2, thirds, quarters, fifths, and tenths.

ETA: Oops -forgot one!! powers of 2 up to 2^10=1024. :)

All these. We also skip count by 12,'s 15's, and 24's and do conversions for eighths and sixteenths.. and go to 2^15 (though I only require memorizing 2^5=32 and 2^10=1024... the rest is just a doubling exercise so the numbers are familiar). And primes through 200: "Quick! Circle the primes on these two hundreds charts!"

I pick two topics a day for practice during morning warm-up, plus one formula.

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