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Slide Notes



Would math be easier if we had more fingers?




Multiplication By Chunking

Published on Nov 19, 2015

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PRESENTATION OUTLINE

2-DIGIT MULTIPLICATION

CHUNKING


Would math be easier if we had more fingers?




Photo by mrehan

18 X 14

FIND THE PRODUCT
Multiplication can be thought of as repeated addition.

In this problem, you might think of 18 groups of 14 being added together one at a time.



Photo by liquidnight

REPEATED ADDITION

18 GROUPS OF 14

I bet she's thinking about using that calculator.

Even if she decides to use her calculator, she'll have to keep up with each addition so that she performs exactly 18 of them.



Photo by Steven Leith

PENCILS PLEASE

NO CALCULATOR

NO CALCULATORS!!!

Does this mean that we'll have to keep adding 14 until we've added all 18 addends?

By the way, I've forgotten why we are multiplying 18 times 14. We'll get back to that later.

Photo by Bilal Lashari

14+14+14+14+...

NOT!

Even with the calculator, we'd have to be sure to enter 14 exactly 18 times.
Photo by angelsk

LET'S CHUNK.


Let's gather larger groups of 14 together so we don't have to perform so many additions.

Let's CHUNK!
Photo by Leo Reynolds

GROUP 10CHUNKS OF 14

THAT'S 140
I like 10 because it is a friendly number to add, subtract, multiply, or divide by.

Let's add 10 chunks of 14 together.
Photo by onezilla

ADD 5 MORE CHUNKS

THAT'S 70 MORE (140+70+?)
Five is another friendly number in multiplication. I know my multiples of five.

And five is half of ten.
Photo by Leo Reynolds

ADD 2 CHUNKS

THAT'S 28 MORE (140+70+28+?)
Those twos are also friendly numbers. Multiplying by two is the same as doubling a number.
Photo by Leo Reynolds

ADD 1 CHUNK

THAT'S 14 MORE (140+70+28+14)
Photo by Leo Reynolds

18 X 14 = 252

THE PRODUCT IS 252.

We're done! Did anybody do this a different way?

Photo by Sean MacEntee

RECAP:

  • Start with 10 chunks of 14
  • Add a friendly 5 chunks.
  • Add 2 more chunks.
  • Add 1 last chunk.
Photo by andyrusch