Double Century

Making 100 with Tens and Ones

Part of: Understanding the Number 100

100 is a special number made of 10 bundles of 10 items each. You can show 100 using sticks, beads, seeds or tokens. For example, 70 sticks bundled in groups of 10, plus 30 single sticks, makes 100. There are many ways to split 100 into a bigger group and a smaller group.

Why it matters. Learning to make 100 helps children understand place value deeply. When children see that 100 = 60 + 40 or 100 = 75 + 25, they grasp that the same quantity can be broken into parts in many ways. This is the foundation for addition and subtraction.

Try at home. Use coins, seeds, or any small objects. Hide some in one hand and some in another. Tell your child the total is 100. Have them guess how many are in each hand, then check together.

Reading and Writing Numbers from 100 to 200

Part of: Writing Numbers Beyond 100

After 99, the next number is 100 (One Hundred). Numbers continue: 101, 102, 103... and so on. Each three-digit number has three places: hundreds, tens, and ones. In 123, the 1 is in the hundreds place (worth 100), the 2 is in the tens place (worth 20), and the 3 is in the ones place (worth 3). Together, 100 + 20 + 3 = 123.

Why it matters. Understanding three-digit numbers is essential for daily life—telling time, reading prices, counting quantities, and doing arithmetic. Without this, children cannot move forward to larger numbers or master place value for multiplication and division.

Try at home. Take any three-digit number your child sees (on a calendar, price tag, or in a book). Ask them to break it into hundreds, tens, and ones. Make it a hunt for three-digit numbers around the house.

Sequencing Numbers on a Number Line

Part of: Ordering and Comparing Numbers

A number line is a visual way to show numbers in order. Each number has a fixed position. The number line helps us see which number comes next, which is before it, and what numbers fall in between. For example, between 120 and 130, we have 121, 122, 123... up to 129. Number lines make it easier to compare numbers and see patterns.

Why it matters. Using number lines builds strong mental models of how numbers relate to each other. Children learn that numbers have a natural order, and this skill is essential for understanding addition and subtraction as movement along the line. It also prepares children for working with negative numbers and more complex number systems later.

Try at home. Make a number line on a long piece of paper. Label every 10th number (100, 110, 120...). Have your child stick stickers or post-its at random numbers, then read them aloud in order.

Counting in Groups of 5, 10, and 20

Part of: Counting Patterns and Jumps

Instead of counting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, we can count by tens: 10, 20, 30, 40... or by fives: 5, 10, 15, 20... Skip counting is faster and helps us see patterns. For example, counting by 5s always lands on 5 or 0 in the ones place. Counting by 10s always has 0 in the ones place.

Why it matters. Skip counting builds fluency and prepares children for multiplication and division. When children count by 5s or 10s, they recognize patterns that make mental math faster and easier. This skill is practical for telling time (by 5s), counting money (by 10s or 20s), and grouping objects.

Try at home. Use a staircase or steps. Have your child skip-count by fives as they climb (5, 10, 15...), or by tens on another try. Ask: 'How many steps up when we count by 10s to reach 50?'

One More and One Less with Numbers Beyond 100

Part of: Representing Numbers Beyond 100

For any number, 'one more' means the next number in the count, and 'one less' means the previous number. For 125, one more is 126, and one less is 124. This works the same way for all numbers. Even when we cross boundaries (like from 129 to 130, where the tens digit changes), the rule stays the same: add 1 or subtract 1.

Why it matters. Understanding one more and one less is foundational for addition and subtraction. Children see that numbers form a continuous sequence, and each change of 1 affects only the ones place (unless the ones digit is 9, when carrying happens). This prepares children for informal algorithms and mental arithmetic.