Transcript Slide 1

Dividing a Decimal by a Decimal
Lesson 2-5
Dividing a Decimal by a Decimal
• We NEVER want a decimal in the divisor.
– If you have a decimal in the divisor, you need to
bump it over until it is all the way over to the right
of the number.
– Move it the same number of places in the dividend.
Remember… no remainders!
• If you solve a problem and you see a
remainder at the end, you are NOT
done!
– Add a decimal and a zero
– If you already have a decimal point, just
add a zero
• Do not put 2 decimal points in one problem!
Let’s try one together…
We cannot have
a decimal point
in the divisor!
Let’s fix it!
We bounced more places
than there were numbers.
This blank represents the
extra spot we bounced.
Turn it into a zero.
1 62 ) 13 2 0
We need to bounce
this decimal point
until it is all the way
to the right of the
divisor.
Since we bounced
the decimal point in
the divisor, we have
to bounce it the same
number of places in
the dividend.
162
150 ) 1320
Is this divisor, 162, closest
to 100?
200?
After
you 150?
have or
bounced
the decimal point in both
the divisor and the
dividend, you can
eliminate the new decimal
point in the divisor.
Does 150 go into 132?
162 is closest to 150. I
am going to use 150 to
estimate how many times
162 will go into my
No, 150 is too big. I need
dividend.
to use oneto
more
digit ofthe
When you do long division, it is easiest
solve
the dividend then.
problem when you estimate using
Insteadyour
of 132,divisor.
I will use
1320.
162
150 ) 1320
Use your fingers to
cover over the last
digit of both the
dividend and the
divisor.
15 x 2 = 30
If I double that (x4), that
would be 60. If I double that
(x 8) would be 120. If I add 15
more to 120, I would have
more than 132, so I should
stop at “times 8.”
Now ask yourself:
Remember
that we are only using the 150 to estimate!
“how many times
does 15 go into
132?”
81
162 ) 1320 0
- 1296
24 0
- 16 2
78
I know that 162 x 2 is greater
than 300. That is too big!
Instead, I will use 1 as the
next number in my quotient.
8 14
162
150 ) 1320 0 0
- 1296
24 0
- 16 2
78 0
- 64 8
132
I am going
150 again…
162 to
x 5use
= 810.
150isx too
2 =big!
300 Let me
Nope! That
If I double
(x 4), I have
try onethat
smaller…
600.
If I add another
(that would
162 x 4 150
= 648
be x5),
then
750. I will
I will
useI have
this one.
try that first.
8 1 48
162
150 ) 1320 0 0 0
- 1296
24 0
- 16 2
78 0
- 64 8
13 2 0
- 12 9 6
I see that my new difference is
the same three numbers as in
my dividend. I will use 8
again…
8 1 48
162 ) 1320 0 0 0
I am rounding to the
My division problem seems to
hundredths place so I
go on and on. I am going to
underlined the four. I look at
stop.
the number to the right of my
underline: the 8. Since 8 is
Instead, I am going to round
bigger than 4, I will add one to
my quotient to the hundredths
my underlined number.
place.
8.148
8.15
Things to remember…
• You can never have a decimal point outside
the division sign
– Bounce the outside decimal all the way to the right
– Count up the number of places you bounced
– Bounce the inside decimal as many times as you did
the outside.
• If you do not have a decimal point, add one to the end of
the number
• If you do not have enough places, then add zeros to the
end of a decimal to make more places
• After the decimal point has been bounced in
both places, divide as usual.