Lesson

When we start to work with larger numbers, it helps to have some different strategies to use, including the area method, partitioning and long multiplication. Let's review a strategy with smaller numbers, so then we can use it with larger numbers.

Calculate 10\times 18 by completing an area model.

a

Firstly, complete the missing values in the area model.

\times | 10 |
---|---|

10 | |

8 |

Worked Solution

b

Now add the values you found in part (a) to calculate 10\times 18.

Worked Solution

Idea summary

We can use an area model to multiply 2 two digit numbers.

If we are multiplying a number in the thousands, look out for some ways to make it easier, like we do in this video.

Find 2\times 869.

Worked Solution

Idea summary

The standard algorithm method is useful for multiplying large numbers.

The area model is great, but we can also perform long multiplication. Let's see how they compare.

Find 739 \times 63.

Worked Solution

Idea summary

As our numbers get larger, it might be easier to use long multiplication. We can still use the area method and partitioning, but long multiplication allows us to set out our problem more easily.

The words and the context they're used in can give us clues to how we need to tackle a problem.

A rock climber descends from the top of a cliff face to the ground in 5 stages, dropping 106 metres each time.

What is the height of the cliff face?

Worked Solution

Idea summary

When we have a written problem, all we need to do is find the keywords to help us understand what we need to work out.

selects and applies appropriate strategies for multiplication and division, and applies the order of operations to calculations involving more than one operation

analyses and creates geometric and number patterns, constructs and completes number sentences, and locates points on the Cartesian plane