Dividing by
decimals
Mr. Johnk 2015
•
3
4
=
30
40
=
300
400
• Each of the fractions are equivalent
•
•
3 10 30
x =
4 10 40
10
=1
10
x
10
10
=
300
400
• Any number multiplied by 1 equals that same number!
•
3
4
means 3 ÷ 4
• 3 ÷ 4 can be written
43
• So when we divide by decimals, we just multiply our divisor by
10, 100, 1,000 or some other power of ten to make it a whole
number.
Whatever you multiply
your divisor by, you
must also do to the
dividend!
divisor dividend
The shortcut is to just move the decimal the
same number of places on each number!
• 64.24 ÷ 0.4
Place the decimal
straight up in the
● quotient
0.4 64.24
You multiplied by
10 so the decimal
is now between
the 2 and 4.
Now just divide 642.4 by 4!
Decimal out of
sight-decimal to
the right!
• 525 ÷ 1.25
• Should our answer get
bigger or smaller?
●
• 1.25 525 0 0●
4 20●
125 52500 ●
-500
250
- 250
00
The answer got smaller!
• However many times you move the decimal to the right
on the outside, is how many times you have to move it on
the inside!
• How many places would you move the decimal in 76.325
÷ 0.0357?
• The answer is?
• 4 places on each number.
• You would need to annex a zero behind the 76325
How many places this time?
87.532 ÷ 0.31
The answer is 2 places! The 0.31
would become 31 and the 87.532
would become 8753.2!