Add and Subtract Mentally a 'Near Multiple of 10' to Or from a Two-Digit Number
Year 4 KO Reference e
Add and subtract mentally a 'near multiple of 10' to or from a two-digit number.
5. Work out 38 + 9
17. Work out 46 + 19
Key Words
Minus, subtract, take away, add, addition, plus, add 10/subtract 1, subtract 10/add 1, two digit number.
Key Questions
How did you work it out?
Are there any ‘clues’ in the numbers that can help you?
What do you notice when you add 9, 19, 99 etc. to a number?
Practical Activities
Strategies to include the use of number lines and number squares to illustrate :
‘When adding 9 : add 10, subtract 1, when subtracting 19 – subtract 20, add 1 etc.’
Role play based on everyday word problems.
Money problems/shopping lists; (items costing amounts such as a pencil for 59p, a bar of chocolate for 31p, an ice lolly for 39p or a book for £1.18). Ask the pupils; ‘How much would it be to buy the ….. and the …..
Use of the blackboard/whiteboard to talk about the sums. Ask pupils to say how they would solve the problem, step by step.
Encourage the pupils to think if their answer is reasonable and to check their answers.
Use of whiteboards to perform addition/subtraction; remember these can be photocopied and individual pupil’s work can then be placed in their workbooks.
*Remember to add 3 or 4 numbers as well*
Another strategy may be …
*When adding, add tens first, then units e.g. 46 + 19 = add 40 + 10 then 9 + 6
Written Activities
Activities to link with the above practical activities & to practice strategies,
for example; 39 + 18, pupils to try … 39 + 20 – 2 = ……
or 150 – 139, pupils to try … 150 – 140 + 1 = …
or adding tens first, then units (see above).
The children can be encouraged to make up their own calculations – any of the above.
IT
:
Maths Pack 2 : Sum Flash Addition, Sum Flash Subtraction
Maths Pack 3 : Addition Facts 1 & 2, Subtraction Facts
Primary Games Vol 1 : Darts (including worksheets)
Primary Games Vol 2 : Sum Sense and Speed Grid Challenge
Primary Games Vol 3 : Hexabonds (including supporting worksheets)
Teaching Money : Money Machine/Coin Drag/Count Up/Change Please
(worksheets/interactive screens)
NNS ITP : ‘Number grid’ and ‘Number line’
Games
The pupils like to have 10 sums and an agreed time to complete them. They like to swap their work with others and to mark out of 10 – full marks or nine out of ten can earn a sticker!
Home activities/Homework
Activities to develop skills in addition/subtraction. A Maths Sack could be put together with suitable resources in – whiteboard, number line, dominoes, cards, dice etc for the pupils to take home. Suggested activities could also be included. Specifically relating to this learning objective – a prompt sheet for parents could be devised; what strategies to use etc.
Springboard 4
Unit 9
Pages 106 - 115
4KOe