Patterns in addition and subtraction II
Patterns to help us
LOOKING FOR change
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.
add or subtract?
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!
regrouping
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:
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.
Worked Examples
Question 1
$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=
Question 2
$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
Question 3
Complete the pattern below.
$643$643 $\editable{}$ $657$657 $\editable{}$