DECIMAL2

1. 61.4
78.9 + 39.2
Decimals
ADDITIONITION AND SUBTRACTION

2. Adding or Subtracting Decimals
 Write the numbers in a vertical column, aligning digits
according to their places.
 Attach extra zeros to the right end of each number so
each number has the same quantity of digits.
 Add or subtract as though the numbers are whole
numbers.
 Place the decimal point in the sum or difference to align
with the decimal point in the respective operation.

3. Adding Decimals
Add the hundredths. There are 16 hundredths.
• Since 16 hundredths is 1 tenth 6 hundredths, write 6 in the
hundredths place. Write 1 as an addend in the tenths place.
2 1
8.784
2.560
+ 6.721
Add up the thousandths. There are 5
thousandth.
Add the tenths. There are 20 tenths.
• Since 20 hundredths is 2 ones 0 tenths, write 0 in the tenths
place. Write 2 as an addend in the ones place.
Add the ones. There are 18 ones.
So 8.784 + 2.56 + 6.721 = 18.065.

4. Subtracting Decimals
4.040
-2.681
1.359
number of the hundredths from 4 to 3 and the number
of thousandths from 0 to 10.
Now subtract. There are 9 thousandths.
Try to subtract the hundredths. You will need more
hundredths.
•There are no tenths to use, so use a one. Change the number
of ones from 4 to 3. Raise the number of tenths from 0 to 9
and the number of hundredths from 3 to 13.
To subtract the thousandths, you will need more
thousandths.
• Use one of the hundredths.
• Since 1 hundredth = 10 thousandths, change the
Subtract the hundredths. There are 5 hundredths.
Subtract the tenths. There are 3 tenths.
Subtract the ones. There is 1 one.
So, 4.040 – 2.681 = 1.359
9 13 10

5. Comparing & Converting
Fractions & Decimals
To convert a fraction  decimal
 Steps
1. Divide the numerator of the fraction by the denominator
2. Round the quotient to a desired place value
Example
 Convert 3/7 to a decimal and round to nearest
Hundredth and Thousandth
 = 0.42857
 Nearest Hundredth: 0.43
 Nearest Thousandth: 0.429

6. To convert a decimal  fraction
Steps
1. Count the number of decimal places
2. Remove the decimal point (and any leading zeros)
3. Put the decimal part over a denominator,
– The denominator is a factor of 10 that has the same number of
zeros as decimal places (from step 1)
4. Put the fraction in simplest form
 Example
 Convert 0.47 to a fraction
 = 47/100
 Convert 0.275 to a fraction
 275/1000 = 11/40
Comparing & Converting
Fractions & Decimals