Lesson 25 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 ID: 660782
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Slide1
Dividing a Decimal by a Decimal
Lesson 2-5Slide2
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.Slide3
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!Slide4
Let’s try one together…Slide5
) 13 2
1 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.
0Slide6
) 1320
162
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.
150Slide7
) 1320
162
150
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 = 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.”Slide8
) 1320
162
8
- 1296
24
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 2
78Slide9
) 1320
162
8
- 1296
24
0
0
1
- 16 2
78
0
150
0
4
I am going to use 150 again…
150 x 2 = 300
If 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 = 648
I will use this one.
- 64 8
132Slide10
) 1320
162
8
- 1296
24
0
0
1
- 16 2
78
0
150
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
8Slide11
) 1320
162
8
0
1
0
4
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.
0
8
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.
8.15Slide12
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.