1. DECIMAL NUMBERS

2. Introduction to Decimal Numbers
A number written as a decimal has 3 parts:
Whole # part
The decimal point
Decimal part
The position of the digit in the decimal number determines the digit’s value.

3. Place Value Chart Whole number part Decimal part Decimal point . tens
ones
tenths
thousands
hundreds
hundredths
thousandths
ten-thousandths
Hundred-thousandths
Whole number part
Decimal part
Decimal point

4. Writing a Decimal Number in Words
Write the whole number part
The decimal point is written “and”
Write the decimal part as if it were a whole number
Write the place value of the last digit
Ex: Write 6.32 in words
Six
and
thirty-two
hundredths

5. Ex: Write 0.276 in words Zero and two hundred seventy-six thousandths
Or two hundred seventy-six thousandths

6. Writing Decimal Numbers in Standard Form
Write the whole number part
Replace “and” with a decimal point
Write the decimal part so that the last non-zero digit is in the identified decimal place value
Note: if there is no “and”, then the number has no whole number part.

7. Ex: Write in standard form “seven hundred sixty-two thousandths”
Ex: Write in standard form “eight and three hundred four ten-thousandths” 8 .
Ex: Write in standard form “seven hundred sixty-two thousandths”
Note: no “and”  no whole part
0 .

8. Your turn to try a few

9. Decimal Addition & Subtraction
To add and subtract decimal numbers, use a vertical arrangement lining up the decimal points (which in turn lines up the place values.)
Ex: Add
put in 0 place holders
16.113
15.21 +
2.0036 3 3 . 3 2 6 6

10. put in the decimal point 16 . 0000 - 9.6413 put in 0 place holders
Ex: Subtract – 19.61 1 1 3 1
24.024
put in 0 place holders -
19.61 4 . 4 1 4
Ex: Subtract 16 – 1 9 9 9 5 1
put in the decimal point 16 .
0000 -
9.6413
put in 0 place holders 6 . 3 5 8 7

11. Your turn to try a few

12. Decimal Multiplication
Decimal numbers are multiplied as if they were whole numbers. The decimal point is placed in the product so that the number of decimal places in the product is equal to the sum of the decimal places in the factors.

13. Ex: Multiply 1.2 x 0.04
Think 12 x 4
 12 x 4 = 48
1.2 has 1 decimal place
0.04 has 2 decimal places
Therefore the product of 1.2 and 0.04 will have = 3 decimal places 48 .
 1.2 x 0.04 = 0.048

14. Ex: Multiply 3.1 x 1.45
Think 31 x 145
 31 x 145 =4495
3.1 has 1 decimal place
1.45 has 2 decimal places
Therefore the product of 3.1 and 1.45 will have = 3 decimal places .
 3.1 x 1.45 = 4.495