dividing a decimal by a decimal lesson 2-5. dividing a decimal by a decimal we never want a decimal...
TRANSCRIPT
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…
) 13 21 62
We cannot have a decimal point in the divisor!
Let’s fix it!
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.
We bounced more places than there were numbers. This blank represents the extra spot we bounced.
Turn it into a zero.
0
) 1320162
When you do long division, it is easiest to solve the problem when you estimate using your divisor.
After you have bounced the decimal point in both
the divisor and the dividend, you can
eliminate the new decimal point in the divisor.
Is this divisor, 162, closest to 100? 150? or 200?
162 is closest to 150. I am going to use 150 to
estimate how many times 162 will go into my
dividend.
Does 150 go into 132?
No, 150 is too big. I need to use one more digit of
the dividend then. Instead of 132, I will use
1320.
150
) 1320162150
Remember that we are only using the 150 to estimate!
Use your fingers to cover over the last
digit of both the dividend and the
divisor.
Now ask yourself: “how many times does 15 go into
132?”
15 x 2 = 30If 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.”
) 13201628
- 129624
0
0
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.
1
- 16 278
) 13201628
- 129624
0
0
1
- 16 278
0150
0
4I am going to use 150 again…
150 x 2 = 300If I double that (x 4), I have
600.If I add another 150 (that would be x5), then I have 750. I will
try that first.
162 x 5 = 810.
Nope! That is too big! Let me try one smaller…
162 x 4 = 648I will use this one.
- 64 8 132
) 13201628
- 129624
0
0
1
- 16 278
0150
0
4
I see that my new difference is the same three numbers as in
my dividend. I will use 8 again…
- 64 8 13 2
0
0- 12 9 6
2 4
8
) 13201628
01
04
My division problem seems to go on and on. I am going to
stop.
Instead, I am going to round my quotient to the hundredths
place.
08
8.148
I am rounding to the hundredths place so I
underlined the four. I look at the number to the right of my underline: the 8. Since 8 is
bigger than 4, I will add one to my underlined number.
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.