Multiplying and dividing
by 10 and 100 is easy…..
…when you know how!
Make sure you keep an eye on the
place – value markers…they’re
REALLY important.
Th
H
T
3
U
2
.
.
t
1
h
0
Multiply it by 10, so every digit becomes 10 times
BIGGER. EVERY digit moves one place to the LEFT.
Th
H
3
T
3
2
U
2
1
.
.
.
t
1
0
h
0
Lets look at that again…






We’ll multiply 56.03 by 10.
Remember what happens to EACH
digit.
Th H T U . t h
5 6 . 0 3
X10
5 6 0 . 3
Check that the order of the digits is
the same as when you started.
So what happens when you
multiply by 100…let’s see




TH H T U . t h
4 6 . 0 2
4
6 0 2 .
X 100
See! Each digit moves across two places
to the left…and of course
100 has 2 zeros, so that’s a good reminder.
The number becomes 100 times bigger
Now if you make numbers bigger by
moving them to the left…what do you
think happens when you divide numbers
by 10?


Yes… you move each digit one place to the
right, to make it 10 times smaller!
Like this…

TH H T U . t
3 5 0 . 0

3 5 . 0


h
0
REALLY IMPORTANT!!!!!!!!!! See how the decimal point stays
inn the same place.
So now you can guess what
happens when you divide by
100.






That’s right, every digit moves two places to
the right to make the number 100 times
smaller.
Lets divide 12.6 into 100 bits…wow how tiny
would each bit be?
TH H T U . t h th t.th
1 2 . 6 0
divided by 100
0 . 1 2 6 0
So 0.1260 is 100 times smaller than 12.6