We’ll start with the easy stuff.
Multiplying by 4:
(1) Double the multiplicand you want to multiply 4 by
(2) Double it one more time
e.g. 8 * 4 = 32
8 * 2 = 16
16 * 2 = 32
Why does this work?
4 can be broken up into 2 * 2
8 * 4 = 32
8 * (2 * 2) = 32
Thanks to the associative property of multiplication,...
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We’ll start with the easy stuff.
Multiplying by 4:
(1) Double the multiplicand you want to multiply 4 by
(2) Double it one more time
e.g. 8 * 4 = 32
8 * 2 = 16
16 * 2 = 32
Why does this work?
4 can be broken up into 2 * 2
8 * 4 = 32
8 * (2 * 2) = 32
Thanks to the associative property of multiplication,...
read more

Summary: Mental math teaches students to see short, efficient solutions—rather than to blindly follow
the brute-force, cookie-cutter, one-size-fit-all, show-all-your-work procedures taught at school.
To my youngest students, I lie—by omission—that vertical arithmetic does not exist. I can usually get away with it for about a year. Until the school shows them the light...
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Dazzling pocket PCs are aplenty for the children of today. Kids roll into the classroom with iPhones, Blackberries, and various Android devices capable of supporting myriad complex applications. We are living in a wonderful age where handheld computers help us tremendously and continuously. Alongside all of the fancy apps (that allow us to manage everything from our finances to our fantasy football...
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