Number (add/sub)

Hong Kong

Stage 1

Lesson

When we solve number problems, sometimes there are some short cuts we can take, using things we already know. If we notice a pattern in our addition problem, we can use that to solve other problems, just like we've down with $1$1 and $2$2 digit numbers. We can use the same approach with larger numbers too.

Place value is really important, as well as remembering that one side of a number problem must equal the other side, if we have an equal sign. By thinking of a see-saw, we can see how one side has changed, to work out the other side.

Sometimes we may have problems that require a little more detective work! In video 2, we look at some of those, and work how out to identify a pattern. We don't always see an increase in our numbers, this time!

In some cases, our number problem may have regrouping, so let's have a look if our pattern still works. We also work through a subtraction problem, with regrouping. Will out pattern still work? Watch this video to find out:

Remember!

By looking at which digits have changed, we may not need to solve the problem fully. Making a change in the same place value column is often what we need to do.

$113+20=133$113+20=133

Use this to find:

$113+30=\editable{}$113+30=

$113+40=\editable{}$113+40=

$113+50=\editable{}$113+50=

$113+70=\editable{}$113+70=

$765+104=869$765+104=869.

Use this to fill in the gaps in the number sentences.

$665+\editable{}=869$665+=869

$565+\editable{}=869$565+=869

Complete the pattern below.

$643$643 $\editable{}$ $657$657 $\editable{}$