Lesson 1 Decimal Numbers

    • Let’s learn about decimals.

Warm-up Notice and Wonder: Shaded Grid

What do you notice? What do you wonder?

hundredths grid. 6 squares shaded.

Activity 1 Shady Fractions

Each large square represents 1.

Problem 1

What fraction do the shaded parts of each diagram represent? For the last square, shade in some parts and name the fraction it represents.

  1. Hundredths grid. 5 squares shaded.
  2. Hundredths grid. 63 squares shaded.
  3. Hundredths grid. 30 squares shaded.
  4. Hundredths grid. All 100 squares shaded.
  5. Hundredths grid. 97 squares shaded.
  6. Hundredths grid. 0 square shaded.

Problem 2

The shaded part of this diagram represents 0.01 or “1 hundredth.”

hundredths grid. 1 square shaded.

  The shaded parts of this diagram represent 0.10 or “10 hundredths.” They also represent 0.1 or “1 tenth.”

hundredths grid. 10 squares shaded

Numbers like 0.01, 0.10, and 0.1 are written as decimals.

Look at the shaded parts of each diagram in the first problem. Write the numbers they represent as decimals.

Problem 3

What fraction and decimal do the shaded parts of each diagram represent?

  1. 2 hundredths grids. First grid, all 100 squares shaded. Second grid, 33 squares shaded.
  2. 2 hundredths grids. First grid, all 100 squares shaded. Second grid, 20 squares shaded.

Activity 2 Ways to Express a Number

Each large square represents 1.

Problem 1

Write a fraction and a decimal that represent the shaded parts of each diagram. Then, write each amount in words.

  1. hundredths grid. 2 squares shaded.
  2. Hundredths grid. 22 squares shaded.
  3. Hundredths grid. 79 squares shaded.

Problem 2

Shade each diagram to represent each given fraction or decimal.

  1. Hundredths grid. No squares shaded

    Fraction:

    Decimal: 0.78

  2. hundredths grid. No squares shaded.

    Fraction:

    Decimal:

  3. Hundredths grid. No squares shaded.

    Fraction:

    Decimal:

  4. 2 hundredths grids. No squares shaded.

    Fraction:

    Decimal:

  5. 2 hundredths grids. no squares shaded.

    Fraction:

    Decimal: 1.6

Problem 3

Han and Elena disagree about what number the shaded portion represents.

Han says that it represents 0.60 and Elena says it represents 0.6.

Explain why both Han and Elena are correct.

hundredths grid. 60 squares shaded

Practice Problem

Problem 1

Each large square represents 1.

  1. Write a fraction and a decimal that represent the shaded part of the large square.

    Hundreds diagram. Fifty three of one hundred shaded.

    Fraction:

    Decimal:

  2. Shade a part of each square to represent each given number.

    Hundreds diagram. 

    Fraction:

    Decimal:

    Hundredths grid. 0 square shaded.

    Fraction:

    Decimal: 0.44