# Transcript: Multiplying Decimal Numbers

Teacher Sarah stands in a studio next to a large touchscreen. She has short brown hair and wears a blue shirt with a print that reads "Homework zone."

A chart appears on the large touchscreen. The columns read "Hundreds, tens, ones, decimal, tenths, hundredths, thousandths."

A caption reads "Teacher Sarah."

Sarah says HI, TVO KIDS.

I'M TEACHER SARAH.

AND TODAY WE'RE GOING TO TALK

ABOUT MULTIPLYING DECIMAL

NUMBERS BY POWERS OF TENTHS.

THAT JUST MEANS MULTIPLYING

DECIMALS BY TENTHS,

HUNDREDTHS AND THOUSANDTHS.

LET'S GET STARTED.

HERE WE HAVE OUR

ORIGINAL NUMBER.

She points at the number 4.2, written on the table as 4 in ones, point in decimal and 2 in tenths.

She says THIS NUMBER IS FOUR

AND TWO TENTHS.

NOW LET'S SAY I WANTED TO

MULTIPLY FOUR AND TWO TENTHS

BY ONE TENTH.

I'M GOING TO TEACH YOU

A VERY EASY TRICK.

ALL WE HAVE TO DO IS TAKE A

LOOK AT OUR POWERS OF TENTH

AND FIGURE OUT HOW MANY PLACES

THERE ARE

AFTER

THE DECIMAL.

LET'S TAKE A LOOK.

HERE, FOR ONE TENTH,

NOTICE I HAVE ONE PLACE

AFTER THE DECIMAL.

SO WHAT THAT MEANS IS NOW

I CAN JUST MOVE MY DECIMAL

ONE PLACE TO THE LEFT.

HERE WE GO.

On the original number she moves the decimal one place to the left, forming the number .42.

She says BY MOVING IT ONE

PLACE TO THE LEFT,

I GET A PRODUCT OF

FORTY-TWO HUNDREDTHS

OR ZERO DECIMAL FORTY-TWO.

SO NOW LET'S TAKE OUR

SAME ORIGINAL NUMBER,

FOUR AND TWO TENTHS, BUT

THIS TIME WE ARE GOING TO

MULTIPLY BY ONE HUNDREDTH.

SO THE SAME THING, WE

HAVE TO COUNT THE NUMBER

OF PLACES THAT OCCUR

AFTER THE DECIMAL.

HERE WE HAVE ONE AND TWO.

SO WHAT THAT MEANS IS THAT

NOW WE HAVE TO TAKE OUR

DECIMAL AND MOVE IT TWO

PLACES TO THE LEFT.

HERE WE GO.

As she moves the decimal two places to the left she says ONE... TWO.

ADD IN MY ZERO.

She adds a zero and says AND FOUR AND TWO TENTHS

MULTIPLIED BY ONE HUNDREDTH IS

FORTY-TWO THOUSANDTHS OR

ZERO DECIMAL ZERO FOUR TWO.

NOW DON'T BE

ALARMED, TVO KIDS.

USUALLY WHEN WE'RE MULTIPLYING

OUR NUMBERS GET LARGER,

BUT IN THIS CASE WE'RE

MULTIPLYING BY NUMBERS

THAT ARE LESS THAN ONE

SO OUR PRODUCT IS

GOING TO GET SMALLER.

HAPPY MULTIPLYING!

A chart appears on the large touchscreen. The columns read "Hundreds, tens, ones, decimal, tenths, hundredths, thousandths."

A caption reads "Teacher Sarah."

Sarah says HI, TVO KIDS.

I'M TEACHER SARAH.

AND TODAY WE'RE GOING TO TALK

ABOUT MULTIPLYING DECIMAL

NUMBERS BY POWERS OF TENTHS.

THAT JUST MEANS MULTIPLYING

DECIMALS BY TENTHS,

HUNDREDTHS AND THOUSANDTHS.

LET'S GET STARTED.

HERE WE HAVE OUR

ORIGINAL NUMBER.

She points at the number 4.2, written on the table as 4 in ones, point in decimal and 2 in tenths.

She says THIS NUMBER IS FOUR

AND TWO TENTHS.

NOW LET'S SAY I WANTED TO

MULTIPLY FOUR AND TWO TENTHS

BY ONE TENTH.

I'M GOING TO TEACH YOU

A VERY EASY TRICK.

ALL WE HAVE TO DO IS TAKE A

LOOK AT OUR POWERS OF TENTH

AND FIGURE OUT HOW MANY PLACES

THERE ARE

AFTER

THE DECIMAL.

LET'S TAKE A LOOK.

HERE, FOR ONE TENTH,

NOTICE I HAVE ONE PLACE

AFTER THE DECIMAL.

SO WHAT THAT MEANS IS NOW

I CAN JUST MOVE MY DECIMAL

ONE PLACE TO THE LEFT.

HERE WE GO.

On the original number she moves the decimal one place to the left, forming the number .42.

She says BY MOVING IT ONE

PLACE TO THE LEFT,

I GET A PRODUCT OF

FORTY-TWO HUNDREDTHS

OR ZERO DECIMAL FORTY-TWO.

SO NOW LET'S TAKE OUR

SAME ORIGINAL NUMBER,

FOUR AND TWO TENTHS, BUT

THIS TIME WE ARE GOING TO

MULTIPLY BY ONE HUNDREDTH.

SO THE SAME THING, WE

HAVE TO COUNT THE NUMBER

OF PLACES THAT OCCUR

AFTER THE DECIMAL.

HERE WE HAVE ONE AND TWO.

SO WHAT THAT MEANS IS THAT

NOW WE HAVE TO TAKE OUR

DECIMAL AND MOVE IT TWO

PLACES TO THE LEFT.

HERE WE GO.

As she moves the decimal two places to the left she says ONE... TWO.

ADD IN MY ZERO.

She adds a zero and says AND FOUR AND TWO TENTHS

MULTIPLIED BY ONE HUNDREDTH IS

FORTY-TWO THOUSANDTHS OR

ZERO DECIMAL ZERO FOUR TWO.

NOW DON'T BE

ALARMED, TVO KIDS.

USUALLY WHEN WE'RE MULTIPLYING

OUR NUMBERS GET LARGER,

BUT IN THIS CASE WE'RE

MULTIPLYING BY NUMBERS

THAT ARE LESS THAN ONE

SO OUR PRODUCT IS

GOING TO GET SMALLER.

HAPPY MULTIPLYING!

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