Introduction to decimals

In this lesson, we will learn:

• Decimals are numbers with place values even smaller than the ones place
• How to use base ten (block) models to represent a decimal's place values (ones place, tenths place, hundredths place) using hundred blocks, tens sticks, and single blocks
• How to write decimals in standard, expanded, and written forms.

Notes:

• Decimals are numbers with place values even smaller than the ones place.
• You can write a decimal point (.) at the end of any whole number
• Writing digits to the right of the decimal point gives decimal place values

Ex. 1.5 shows decimal place of tenths; 2.64 shows decimal place of hundredths
• The names of decimal place values mirror the names of whole number place values, but you need to add the "-ths" suffix to the end.
• Each place value is 10 times MORE than the place on its right
• Each place value is 10 times LESS than the place on its left

Ex. 111.11



hundreds	tens	one	.	tenths	hundredths
1	1	1	.	1	1
=100	=10	=1		=0.1	=0.01



• Decimals can be represented with base ten (block) models
• "One whole" or hundred block = ones place value
• Column or stick = tenths place value
• Single square = hundredths place value

Ex. 1.25

• Decimals can be written in standard, expanded, and written forms:
• Standard form: the decimal is written with number digits and a decimal point
• Expanded form: the decimal is written as a sum of values for all place values
• Written form: the decimal is written with words naming digits and place values from left to right

Ex. 12.34 (read aloud as "twelve point three four")




Standard form:	12.34
Expanded form:	10 + 2 + 0.3 + 0.04
Written form:	twelve and three tenths four hundredths OR twelve and thirty-four hundredths



• Trailing zeroes (at the end/right of the number) are NOT important in decimals
• Ex. 0.5 and 0.50 are equal (5 tenths = 50 hundredths)