BASIC CONCEPTS 5.NBT.3
Reading and Writing Decimals
Purpose:
To read and write decimals and illustrate place value
Materials:
Decimal Squares and Decimal Place Value Tables (attached)
TEACHER MODELING/STUDENT COMMUNICATION
Activity 1 Writing decimals and their names
Decimal
Squares
pencils
and paper
1a. Spread the squares face down and select any red square.
Write a description of the square giving the total number of
parts and the number of shaded parts. Write the decimal for
the square and its name. (This square has 8 out of 10 parts
shaded, its decimal is .8, and its name is eight tenths.)
eight tenths
b. How is the total number of parts for a red square
related to the name of the decimal for the square? (A red
square has 10 equal parts and its decimal is tenths. Also,
the decimal for a red square has one decimal place.)
2a. Select any green square, write a description of
the square, its decimal, and the name of the decimal.
(This square has 35 out of 100 parts shaded, its
decimal is .35, and its name is thirty-five hundredths.)
thirty-five hundredths
b. How is the total number of parts for a green square related to the name of the decimal for
the square? (A green square has 100 equal parts and its decimal is hundredths. Also, the
decimal for a green square has two decimal places.)
c. What is the decimal for a green square with 5 shaded parts? (.05) Discuss the need for the
zero in ".05" and that the decimals for hundredths need two decimal places. Also, .5 cannot
be used for this square because it is the decimal for 5 parts out of 10.)
3a. Select any yellow square, write a description of the
square, its decimal, and the name of the decimal. (This
square has 475 out of 1000 parts shaded, its decimal is .475,
and its name is four hundred seventy-five thousandths.)
four hundred seventy-five thousandths
b. How is the total number of parts for a yellow square related to the name of the decimal
for the square? (A yellow square has 1000 equal parts and its decimal is thousandths. Also,
the decimal for a yellow square has three decimal places.)
c. What is the decimal for a yellow square with 5 shaded parts, 50 shaded parts or 75 shaded
parts? (.005, .050, and .075 because the decimals for thousandths have three decimals places.)
4. Select a square of any color and write the name of its decimal. What information is
given by the two parts of each decimal's name? (The first part tells the number of
shaded parts in a square and the second tells the total number of equal parts.)
Activity 2 Place values for decimals
1. Distribute Decimal Place Value Tables to each student.
Decimal
Squares
Decimal
Place
Value
Tables
a. Find a green square with 45 parts shaded. What is the name of
its decimal? (Forty-five hundredths) Why can we think of this
square as having 4 tenths and 5 hundredths? (Because it has 4
full columns shaded and 5 more hundredths.)
.45
b. Write the digits for .45 in a place value table. What digit
should be written in the tenths column of the table? (4) What
digit should be written in the hundredths column? (5) So for
the decimal .45, we say "4" is in the tenths place and "5" is
in the hundredths place.
2. a. Find a yellow square with 325 parts shaded. What is the
name of its decimal? (Three hundred twenty-five thousandths)
Why can we think of this square as having 3 tenths, 2
hundredths, and 5 thousandths? (Because it has 3 full columns
shaded, 2 more hundredths, and 5 tiny thousandths parts.)
.325
b. Write the digits for .325 in a place value table. What digits
should be written in each column of the table? (3 in the
tenths column, 2 in the hundredths column, and 5 in the
thousandths column.) So for the decimal .325, we say "3" is
in the tenths place, "2" is in the hundredths place, and "5" is
in the thousandths place.
3. Complete place value tables for the decimals of some other squares.
Activity 3 Comparing decimals to thousandths
Decimal
Place
Value
Tables
1. Given the decimals .345 and .342, which is the greater? (.345) Explain your reasoning. (One
explanation is the thousandths square for .345 has 345 shaded parts out of 1000, and the
thousandths square for .342 has only 342 shaded part out of 1000. Another method is comparing
the digits of each place value. Starting with the tenths place, both tenths digits are equal, then
comparing the hundredths digits both are equal, and finally checking the thousandths place the
thousandths digit in .345 is greater than the thousandths digit in .342, so .345 > .342.)
5 > 2 so .345 > .342
2. Write an inequality for each of the following pairs of decimals and explain your reasoning.
Use extra zeros to replace 1-place and 2-place decimals by equal 3-place decimals.
a. .208 and .23
b. .14 and .142
c. .642 and .64
d. .7 and .702
INDEPENDENT PRACTICE and ASSESSMENT
Worksheets 5.NBT.3 #1, #2, #3, #4 and decimalsquares.com Beat the Clock
Decimal Place Value Tables Name:
Date:
.