Year 4

We can multiply and divide mentally, including multiplying by 0 and dividing by 1

Year 4 Unit 7b

What we are learning:

• It is important to understand and remember what happens when we multiply by 0 or divide by 1
• When we multiply any number by 0, the answer is always 0, for example zero lots of 4 is nothing
• To demonstrate this set out 4 and then remove them to show that if you had no piles of 4 you would have nothing
• When we divide any number by 1 the answer is the number you started with, for example 12 divided into piles of 1 would give you 12 piles of 1 so the answer is 12
• To extend our ability in mental maths we are now multiplying 3 numbers together in our heads

Activities you can do at home:

Write some numbers and then multiply them by 0 and divide them by one.
Use large numbers and numbers with decimals to make it fun.
Now try the same but without writing them down. This will help in remembering how to say large numbers.
Have a go at doing other mental multiplication and division sums, adding in some examples of multiplying by 0 and dividing by 1.

Have a go at these mental multiplication sums and then invent some similar examples for yourself using number facts that you know your child is familiar with:
2x6x5=
3x10x3=
200x3x6=
7x9x100=
Remember these sums can be done in any order, so talk to your child about which order they could do the sums in, which is quicker for them.

Good questions to ask:

What happens to a number when we multiply it by 0?
Does the same happen with any number?
What happens when we divide a number by one?
Does the same happen all the time with any number?
Is there a faster way for you to find the answer?
Which sums can you do without calculating because you already know the answer?

If your child:

Finds it difficult to see the concepts involved
Use real objects to demonstrate and talk together about what is happening.
Test different numbers of objects to see if the rules stay the same.