Sexy Maths

… what could be less sexy than memorizing 4th grade multiplication facts?

Just the facts ,[object Object],[object Object],[object Object]

What helps kids memorize multiplication facts? ,[object Object]

Surprise What is 6  6? What is 5  7?

Surprise What is 6  6? What is 5  7? 36 35

Surprise What is 9  9? What is 8 x 10?

Is this always true? always one more than Is this number times itself

Is this always true? always one more than Is this number times itself the product of these two numbers?

One way to look at it 5  5

One way to look at it 5  4 Removing a column leaves

One way to look at it 6  4 Replacing as a row leaves with one left over.

One way to look at it 6  4 Removing the leftover leaves showing that it is one less than 5  5 .

A second look Removing a column leaves it narrower by 1.

A second look Replacing as a row leaves it narrower by 1 and taller by 1 (with 1 left over).

What’s the gain? ,[object Object],[object Object],[object Object],[object Object],Direct benefit!

What’s the gain? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Investment in the future!

Further Investigation ,[object Object],[object Object]

Experiment a moment ,[object Object]

Experiment a moment … or how 8  8 relates to 6  10…

Experiment a moment … or how 9  9 relates to 7  11…

(7 – 1 ) (7 + 1 ) = 7  7 – 1 ,[object Object],[object Object],[object Object],n n – 1 n + 1

Where does this lead? ,[object Object],[object Object]

Where does this lead? ,[object Object],[object Object],[object Object],[object Object]

Where does this lead? ,[object Object],[object Object],[object Object],[object Object],[object Object]

www 2 .edc.org/mathworkshop Thanks! E. Paul Goldenberg [email_address] Contact Information

www 2 .edc.org/mathworkshop Bye! Thanks! E. Paul Goldenberg [email_address] Contact Information

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