Grade 1

The Human Knowledge Project

Unit 4 — Numbers to 100

Welcome back!

Numbers help us understand the world.

We use numbers every day when we:

Today we will explore numbers all the way to 100.

Counting Forward

Let's count together.

1, 2, 3, 4, 5...

Can you keep going?

Practice counting:

The more you practice, the easier counting becomes.

Counting Backward

Sometimes we count backward.

Try counting:

10, 9, 8, 7...

Now try:

20 down to 1.

Counting backward helps us prepare for subtraction.

Counting by Twos

We do not always count one at a time.

Sometimes we count by twos.

2, 4, 6, 8, 10...

Can you continue?

Counting by twos helps us notice patterns.

Counting by Fives

Now count by fives.

5, 10, 15, 20...

Many clocks count by fives.

Skip counting makes counting faster.

Counting by Tens

Let's count by tens.

10

20

30

40

50

60

70

80

90

100

Counting by tens helps us understand larger numbers.

Finding Patterns

Numbers follow patterns.

Look carefully.

1, 2, 3, 4...

Each number is one larger.

Now look at:

10, 20, 30, 40...

Each number is ten larger.

Finding patterns helps us become better mathematicians.

Comparing Numbers

Sometimes we compare numbers.

Which is greater?

37 or 42?

Which is smaller?

18 or 25?

Learning to compare numbers helps us solve many kinds of problems.

Activity

Write the numbers from 1 to 100.

Now:

Circle every number that ends in 5.

Underline every multiple of 10.

Can you see the patterns?

Practice

Fill in the missing numbers.

18, 19, __, 21, 22

46, __, 48, 49

70, 80, __, 100

2, 4, 6, __, 10

5, 10, __, 20, 25

Review

Today you learned:

Numbers are patterns waiting to be discovered.

Looking Ahead

Next we will explore place value.

You will discover:

Understanding place value makes larger numbers much easier to understand.