# Transcript: Using a Matrix for 2-Digit Multiplication

(music plays)

Sarah stands next to a wall touch screen showing a two-column table and a multiplication example. She is in her mid-twenties, with short straight brown hair. She wears a blue T-shirt with a print that reads "Home Work Zone" and black tights.

She says HI, TVO KIDS,

I'M TEACHER SARAH,

AND TODAY, I'M GOING

TO SHOW YOU

HOW WE CAN USE

THE MATRIX METHOD

OF MULTIPLICATION

FOR TWO

DIGIT NUMBERS.

THE SAME RULES

APPLY.

LET'S START WITH

OUR FIRST NUMBER.

HERE I'M ASKED

TO MULTIPLY 15,

MULTIPLIED

BY 25.

SO I START

BY LOOKING AT

MY FIRST NUMBER,

AND I NEED TO

BREAK IT DOWN

INTO TENS AND ONES.

IF I TAKE A LOOK

AT MY 15,

I SEE THERE IS A

ONE IN THE TEN'S COLUMN,

AND THAT MEANS THAT

THE TOTAL VALUE

OF THAT

DIGIT IS WORTH TEN.

SO I WRITE MY TEN

RIGHT UP HERE.

NOW I NEED TO GO

ON TO THE NEXT DIGIT.

THE DIGIT IN THE

ONES IS A FIVE.

THE TOTAL VALUE OF

THAT DIGIT IS FIVE.

SO I WRITE MY ONES

VALUE RIGHT HERE.

NOW I'M GOING TO

MOVE ON TO MY 25.

I GET TO DO THE

SAME THING.

TAKE A LOOK AND

SEE WHAT NUMBER

IS IN MY TENS

PLACE.

I SEE I

HAVE A TWO.

I KNOW THAT

THAT MEANS

THAT DIGIT

IS WORTH 20.

NOW MOVING ON, I

LOOK AT MY ONES

AND I SEE THAT

THERE IS A FIVE.

SO I WRITE THE VALUE

OF MY ONES HERE.

THE NEXT

THING I DO IS

I MULTIPLY EACH

NUMBER AND

WRITE THE

PRODUCT IN THE COLUMN.

SO TEN, MULTIPLIED

BY 20,

I KNOW ONE

TIMES TWO IS TWO,

AND I KNOW THAT IF

I'M MULTIPLYING

BY TEN,

I ADD ZEROS.

SO I KNOW THAT TEN

MULTIPLIED BY 20

IS GOING TO GIVE

ME A PRODUCT OF 200.

She writes the numbers in purple.

She continues NOW I DO THE SAME

THING HERE.

TEN MULTIPLIED BY

FIVE IS EQUAL TO 50.

I REPEAT THE SAME

PROCESS WITH

MY FIVE.

FIVE MULTIPLIED BY

20 IS EQUAL TO 100.

AND I KNOW THAT

FIVE MULTIPLIED

BY FIVE IS

EQUAL TO 25.

THE LAST STEP IS

TO ADD UP

THE PRODUCTS

THAT I HAVE IN EACH

OF MY BOXES.

SO I HAVE 200,

PLUS 100,

PLUS 50,

PLUS 25.

I KNOW THAT 200 PLUS

100 IS 300,

300 PLUS 50 IS

350, AND 350 PLUS 25

IS EQUAL TO

375.

SO THERE YOU

HAVE IT, TVO KIDS.

USING THE MATRIX

MULTIPLICATION

METHOD FOR

TWO DIGIT NUMBERS -

15 MULTIPLIED BY 25

IS EQUAL TO 375.

SEE YOU

NEXT TIME!

Sarah stands next to a wall touch screen showing a two-column table and a multiplication example. She is in her mid-twenties, with short straight brown hair. She wears a blue T-shirt with a print that reads "Home Work Zone" and black tights.

She says HI, TVO KIDS,

I'M TEACHER SARAH,

AND TODAY, I'M GOING

TO SHOW YOU

HOW WE CAN USE

THE MATRIX METHOD

OF MULTIPLICATION

FOR TWO

DIGIT NUMBERS.

THE SAME RULES

APPLY.

LET'S START WITH

OUR FIRST NUMBER.

HERE I'M ASKED

TO MULTIPLY 15,

MULTIPLIED

BY 25.

SO I START

BY LOOKING AT

MY FIRST NUMBER,

AND I NEED TO

BREAK IT DOWN

INTO TENS AND ONES.

IF I TAKE A LOOK

AT MY 15,

I SEE THERE IS A

ONE IN THE TEN'S COLUMN,

AND THAT MEANS THAT

THE TOTAL VALUE

OF THAT

DIGIT IS WORTH TEN.

SO I WRITE MY TEN

RIGHT UP HERE.

NOW I NEED TO GO

ON TO THE NEXT DIGIT.

THE DIGIT IN THE

ONES IS A FIVE.

THE TOTAL VALUE OF

THAT DIGIT IS FIVE.

SO I WRITE MY ONES

VALUE RIGHT HERE.

NOW I'M GOING TO

MOVE ON TO MY 25.

I GET TO DO THE

SAME THING.

TAKE A LOOK AND

SEE WHAT NUMBER

IS IN MY TENS

PLACE.

I SEE I

HAVE A TWO.

I KNOW THAT

THAT MEANS

THAT DIGIT

IS WORTH 20.

NOW MOVING ON, I

LOOK AT MY ONES

AND I SEE THAT

THERE IS A FIVE.

SO I WRITE THE VALUE

OF MY ONES HERE.

THE NEXT

THING I DO IS

I MULTIPLY EACH

NUMBER AND

WRITE THE

PRODUCT IN THE COLUMN.

SO TEN, MULTIPLIED

BY 20,

I KNOW ONE

TIMES TWO IS TWO,

AND I KNOW THAT IF

I'M MULTIPLYING

BY TEN,

I ADD ZEROS.

SO I KNOW THAT TEN

MULTIPLIED BY 20

IS GOING TO GIVE

ME A PRODUCT OF 200.

She writes the numbers in purple.

She continues NOW I DO THE SAME

THING HERE.

TEN MULTIPLIED BY

FIVE IS EQUAL TO 50.

I REPEAT THE SAME

PROCESS WITH

MY FIVE.

FIVE MULTIPLIED BY

20 IS EQUAL TO 100.

AND I KNOW THAT

FIVE MULTIPLIED

BY FIVE IS

EQUAL TO 25.

THE LAST STEP IS

TO ADD UP

THE PRODUCTS

THAT I HAVE IN EACH

OF MY BOXES.

SO I HAVE 200,

PLUS 100,

PLUS 50,

PLUS 25.

I KNOW THAT 200 PLUS

100 IS 300,

300 PLUS 50 IS

350, AND 350 PLUS 25

IS EQUAL TO

375.

SO THERE YOU

HAVE IT, TVO KIDS.

USING THE MATRIX

MULTIPLICATION

METHOD FOR

TWO DIGIT NUMBERS -

15 MULTIPLIED BY 25

IS EQUAL TO 375.

SEE YOU

NEXT TIME!

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