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Adding Numbers with 5s and 10s

This lesson shows students how to use 5 and 10 as anchor numbers when adding. It covers the make a ten strategy, ten frame models, and skip counting by 5s and 10s, with worked examples that build toward fluent addition facts up to 20.

Why 5 and 10 are friendly numbers

Some numbers are just easier to work with than others. \(5\) and \(10\) are two of the friendliest numbers in addition because they line up with our fingers, our place value system, and the way ten frames are built. When a problem includes a \(5\) or a \(10\), or when we can turn part of a problem into a \(10\), the rest of the addition becomes much simpler.

This lesson builds on skills from addition facts up to 20 and shows a strategy that makes those facts faster to recall: using \(5\) and \(10\) as anchor numbers.

Making a ten to add

The "make a ten" strategy breaks one addend into two smaller pieces so that one piece completes the other number up to \(10\). Once you reach \(10\), adding the leftover piece is easy.

Here is the idea for \(8 + 5\):

Start with \(8\). Ask how many more are needed to reach \(10\). The answer is \(2\).
Split the \(5\) into \(2 + 3\), because \(2\) is exactly what \(8\) needs to become \(10\).
Add: \(8 + 2 = 10\), then \(10 + 3 = 13\).

So \(8 + 5 = 8 + 2 + 3 = 10 + 3 = 13\). This is often written as "make 10 then add," since the goal is always to build a ten first and finish with the remaining part.

Seeing it with a ten frame

A ten frame is a simple grid of two rows of five boxes. Filling in dots shows exactly how many more are needed to reach \(10\), which makes the make a ten strategy visual instead of abstract.

Six filled boxes and four empty boxes show that \(6 + 4 = 10\).

Once a ten frame is full, any extra dots simply get added on top, which is exactly how the make a ten strategy works with larger sums.

Using a number line to make a ten

A number line makes the two jumps in "make 10 then add" easy to follow: one short jump lands on \(10\), and a second jump covers what is left. This connects directly to the strategy shown in using a number line to add up to 20.

Starting at 8, jump 2 to reach 10, then jump 3 more to land on 13.

Skip counting by 5s and 10s

Adding by 5s and 10s can also mean adding groups of these numbers together quickly, using skip counting instead of counting one at a time. For example:

\(5 + 5 + 5 = 15\), the same as counting "5, 10, 15."
\(10 + 10 + 10 = 30\), the same as counting "10, 20, 30."

This works well alongside the strategies in addition with regrouping up to 20, since grouping numbers into tens is the first step toward regrouping with larger sums.

Worked example

Add \(9 + 6\) using the make a ten strategy.

Ask how many more \(9\) needs to reach \(10\): that is \(1\).
Split \(6\) into \(1 + 5\).
Add: \(9 + 1 = 10\), then \(10 + 5 = 15\).

So \(9 + 6 = 9 + 1 + 5 = 10 + 5 = 15\).

Tips for practicing

Always ask "what does this number need to reach 10?" before splitting the second addend.
Draw a quick ten frame if a problem feels tricky, filling boxes one at a time.
Practice skip counting by 5s and 10s out loud until it feels automatic.
Check answers with simple addition facts, then move on to slightly bigger sums.

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