3. Multiplication strategies

3.01 Repeated addition as multiplication

3.02 Groups and arrays

PRACTICE: x2,4,8

PRACTICE: Multiplication

3.10 Multiply and divide by 10; the powers of 10

Year 4

3.08 x7

Lesson

Ideas

Are you ready?
7 times tables

Are you ready?

Multiplication looks at equally sized groups. Can you solve these multiplication questions?

Examples

Example 1

Find the value of 5\times6.

Worked Solution

Create a strategy

We can think of this as 5 groups of 6, like the image below which has 5 groups of 6 squares.

5 rows of 6 squares.

Apply the idea

The above image has 30 squares in total.

5\times6=30

Example 2

Find the value of 2\times6.

Worked Solution

Create a strategy

We can think of this as 2 groups of 6, like the image below which has 2 groups of 6 stars.

2 circles with 6 stars in each circle.

Apply the idea

The above image has 12 stars in total.

2\times6=12

Idea summary

Thinking of multiplication as equally sized groups of objects can make multiplication easier.

7 times tables

Now let's look at the 7 times tables.

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Examples

Example 3

Find the value of 7\times9.

Worked Solution

Create a strategy

We can think of this as 7 groups of 9, like the image below which has 7 groups of 9 squares.

Seven rows of 9 squares.

Apply the idea

The above image has 63 squares in total.

7\times9=63

Reflect and check

We can also think of this as 5 \times 9+2\times 9.

\displaystyle 5 \times 9	\displaystyle =	\displaystyle 45	Multiply by 5
\displaystyle 2 \times 9	\displaystyle =	\displaystyle 18	Multiply by 2
\displaystyle 7\times 9	\displaystyle =	\displaystyle 45+18	Add the answers
	\displaystyle =	\displaystyle 63

Idea summary

We can use a split strategy to help answer 7 times tables.

7 groups is the same as 5 groups + \ 2 groups.

Outcomes

AC9M4A02

recall and demonstrate proficiency with multiplication facts up to 10 x 10 and related division facts; extend and apply facts to develop efficient mental strategies for computation with larger numbers without a calculator

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