You might notice that sometimes the standard algorithm is called the 'vertical algorithm'. Let's think about why. When we use the standard algorithm, we line our numbers up in 'vertical' place value columns.

Subtraction without regrouping

Let's try some subtraction problems, using the standard algorithm. We use place value models to help us, so you might like to have some handy as you watch the video.

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Examples

Example 2

Find the value of 95 -51.

Worked Solution

Create a strategy

Use the subtraction algorithm.

Apply the idea

Write the subtraction in a vertical algorithm.\begin{array}{c} & &9 &5 \\ &- &5 &1 \\ \hline & \\ \hline \end{array}

Subtract the smallest place value first. So 5 - 1 = 4.\begin{array}{c} & &9 &5 \\ &- &5 &1 \\ \hline & & &4 \\ \hline \end{array}

Then subtract the next place value, 9- 5 = 4.\begin{array}{c} & &9 &5 \\ &- &5 &1 \\ \hline & &4 &4 \\ \hline \end{array}

So, 95- 51 = 44.

Idea summary

When we solve problems using an algorithm, we have to line up our digits by place value. With subtraction, we always put the total at the top, and the number we are subtracting, below.

Outcomes

AC9M3A02

extend and apply knowledge of addition and subtraction facts to 20 to develop efficient mental strategies for computation with larger numbers without a calculator

4.05 Subtraction using algorithm

Ideas

Are you ready?

Examples

Example 1

Subtraction without regrouping

Examples

Example 2

Outcomes

AC9M3A02

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