DECIMAL NUMBERS

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.

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

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

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

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.

Ex: Write in standard form “seven hundred sixty-two thousandths” Ex: Write in standard form “eight and three hundred four ten-thousandths” 8 3 0 4 . Ex: Write in standard form “seven hundred sixty-two thousandths” Note: no “and”  no whole part 7 6 2 0 .

Your turn to try a few

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 16.113 + 15.21 + 2.0036 put in 0 place holders 16.113 15.21 + 2.0036 3 3 . 3 2 6 6

put in the decimal point 16 . 0000 - 9.6413 put in 0 place holders Ex: Subtract 24.024 – 19.61 1 1 3 1 24.024 put in 0 place holders - 19.61 4 . 4 1 4 Ex: Subtract 16 – 9.6413 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

Your turn to try a few

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.

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 1 + 2 = 3 decimal places 48 .  1.2 x 0.04 = 0.048

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 1 + 2 = 3 decimal places 4 4 9 5 .  3.1 x 1.45 = 4.495