# Use knowledge of facts and unitising to add and subtract multiples of ten

I can use knowledge of known facts and unitising to add and subtract multiples of ten.

# Use knowledge of facts and unitising to add and subtract multiples of ten

I can use knowledge of known facts and unitising to add and subtract multiples of ten.

## Lesson details

### Key learning points

- Tens numbers can be added to or subtracted from a multiple of ten.
- When you add a tens number to a multiple of ten the tens number increases.
- When you subtract a tens number from a multiple of ten the tens number decreases.
- If 3 + 1 is equal to 4 then 3 tens + 1 ten is equal to 4 tens which is equal to 40
- If 4 - 1 is equal to 3 then 4 tens subtract 1 ten is equal to 3 tens which is equal to 30

### Common misconception

Children may use counting on and back strategies instead of application of known facts and therefore be inefficient when adding and subtracting multiples of 10

Use representations to make clear links when unitising e.g. adding 2 to 3 and then adding 2 groups of 10 to 3 groups of 10, to support children in making the link. Children should be increasingly fluent in addition and subtraction within 10

### Keywords

Add - To find the total, or sum, by combining two or more parts (addends), or to increase an amount by adding another.

Plus - To find the total, or sum, by combining two or more parts (addends), or to increase an amount by adding another.

Subtract - To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.

Minus - To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Video

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## Starter quiz

### 6 Questions

50

60

40

30

## Exit quiz

### 6 Questions

so 4 tens plus 2 tens is equal to 6 tens.

so 5 tens plus 3 tens is equal to 8 tens.

so 2 tens plus 5 tens is equal to 7 tens.