2. Addition and subtraction

Lesson

Now that we are ready to add large numbers with regrouping, it's worth checking back to make sure we are able to add large numbers where we don't need to regroup .

Find the value of 34\,246+3213.

Worked Solution

Idea summary

You can add numbers in any order, but we often add them with the largest number on the top row.

Zero placeholders are important when we write our digits in a vertical algorithm. For example, 40\,743 would be written as 4743 if we didn't include a zero placeholder

It's time to see how to add large numbers when we do need to do some regrouping. This means we end up with a number more than 9 in one (or more) of our places.

Find the value of 19\,292 + 34\,131.

Worked Solution

Idea summary

When we add, we always start from the digit furthest to the right, and work left. Any time we have more than 9 in any place, we regroup to the place to the left.