 Patterns in addition and subtraction II

Lesson

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.

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:

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.

Worked Examples

Question 1

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

Use this to find:

1. $113+30=\editable{}$113+30=

2. $113+40=\editable{}$113+40=

3. $113+50=\editable{}$113+50=

4. $113+70=\editable{}$113+70=

Question 2

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

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

1. $665+\editable{}=869$665+=869

2. $565+\editable{}=869$565+=869

Question 3

Complete the pattern below.

1.  $643$643 $\editable{}$ $657$657 $\editable{}$

Outcomes

NA3-3

Know counting sequences for whole numbers.

NA3-6

Record and interpret additive and simple multiplicative strategies, using words, diagrams, and symbols, with an understanding of equality