Mental math is one of the most helpful skills one can acquire. Mental math frees you from feeling enslaved
to a calculator. Mental math can make
you feel powerful. Mental math saves
time—it’s more efficient than paper-and-pencil arithmetic. Mental math is
often “good enough” for an answer. And
last but not least, mental math is cool: it
is cool how the mental math works, it’s
cool how helpful the mental math is, it’s
cool how much time it saves, and it’s cool
Yet for many students, mental math is
one of the least acquired skills. How can
mental math be fostered and developed?
Several dynamics come to mind.
1. Basic Facts
Get the basic facts of +, –, x, and ÷
simply flat-out memorized. No matter
where you stand on the use of electronic
calculators, and no matter how early a
student starts using a calculator, it’s still
valuable, even crucial, to have basic
There are three key dynamics to memorization: repetition, repetition, and repetition. Simply repeating, repeating, and
repeating a math fact is all that’s necessary for memorization. Such repetition
can occur in many ways: saying/chanting
basic facts (6x7= 42, 6x7= 42, 6x7= 42),
seeing basic facts, hearing them, writing
them, picturing/imagining them, singing
them, and staring at them. In our house,
we posted basic facts tables on the bathroom wall, so when our kids were sitting
on the throne (ahem!) the basic facts were
in their field of vision. All of these ways
can be part of the repetition-repetition-repetition necessary for memorization
to occur. Keep in mind: memorization
doesn’t make mastery harder; memorization makes mastery possible.
Teach estimation, that 69 x 32 is approximately 70 x 30, which is 7x10 x
3x10, which is 7x3 x 10x10, which is 21 x
100 — so 68 x 33 is approximately 2100.
Likewise, 69 + 32 is approximately 70 +
30, which is 100, so 69 + 32 is about 100.
And 71 – 32 is about 70 – 30, which is 40,
so 71 – 32 is about 40.
Parents, it also is tremendously helpful for you to model out loud your
own mental math with your kids. This
is what’s called talking your walk, explaining what you’re doing while you’re
5. Flexible Thinking
I believe the single most helpful dynamic
for mental math (after basic fact mastery)
is the ability to think of a given quantity
in more than one way. Thinking in sev-
eral and numerous ways. For example,
by Bob Hazen
in the Elementary Grades
It is cool how the mental math works, it’s cool how helpful the mental
math is, it’s cool how much time it saves, and it’s cool being cool.