Year 2 Teaching Sequence Spring 3 – Pairs to 20, solving word problems (three days)

Prerequisites:

; Partition 20 into pairs (see autumn teaching sequence 3 and spring oral and mental starter bank 3)

; Use the = sign to represent equality (e.g. 6 + 4 = 7 + 3) (see autumn teaching sequence 3)

; Recognise the use of a symbol such as ? to represent an unknown (see autumn teaching sequence 3)

Overview of progression:

Children revise partitioning pairs to 20 (using the 20 bead frame) and then record the corresponding addition and subtraction sentences.

They use ‘slidy’ box’ cards to reinforce the idea of an empty box in number sentences. ? and ? are used to stand for

mystery numbers in number sentences. Children go on to solve word problems involving simple addition and subtraction.

Note that the 20 bead frame image previously used in Year 2 has beads in two colours grouping in fives. This helps children to subitise (recognise numbers without counting). The arrangement of 20 in two rows can help children to see the link with pairs to 10, one colour for five, and one for numbers less than or equal to five.

Note that the approach to solving word problems here is to focus on children imagining the whole problem rather than being misled by words such as ‘more than’ when finding a difference is needed rather than addition. They are encouraged to think

what would be necessary to do with the numbers to solve the problem, for example do numbers need to be compared, combined, or one number increased by another? They then identify the operation and calculation necessary to find the numerical answer, before answering the problem itself. Allow lots of time for the discussion at each stage, the actual arithmetic should be a minor part of the session, and is therefore easier than might be in a lesson focused on calculation. ? Original teaching sequence copyright Hamilton Trust, who give permission for it to be adapted as wished by individual users. Y2 Maths TS3 – Spr – 3days

Watch out for children who see that we can reverse additions and get the same answer and think this also applies to subtraction, e.g. 18 + 2 = 20; 2 + 18 = 20, so 20 – 18 = 2 and 18 – 20 = 2, rather than swapping the 18 and 2.

Watch out for children who only understand the equal sign as ‘makes’ rather than a symbol of equality.

Watch out for children who want you to read the problem and work out what calculation to do rather than realising that this is the aim of the sessions!

? Original teaching sequence copyright Hamilton Trust, who give permission for it to be adapted as wished by individual users. Y2 Maths TS3 – Spr – 3days

Objectives:

; Find all pairs with a total of 20 and record the corresponding addition and subtraction facts

; Recognise the use of a symbol such as ? to represent an unknown

; Imagine what action would be needed to solve a word problem and decide what calculation is necessary (addition or

subtraction)

Whole class Group activities Paired/indiv practice Resources Show children the 20 bead frame (two rows of Group of 4-5 children Children work in pairs to shuffle a ; 20 bead frame ten beads). How many beads are there on In advance prepare ‘slidy box’ cards: pack of 0-20 cards, take one and (two rows of

Ask children to 15 + 5 = 20 and 20 – 5 = 15 on the back discuss what needs to be added ten beads with each bar? And altogether?

close their eyes whilst you slide the last three 12 + 8 = 20 and 18 + 2 = 20 to it to make 20. They record the whiteboard) on the bottom row behind the whiteboard. 20 – 2 = 18 and 20 – 18 = 2 addition. They also discuss what ; ‘Slidy box’ Open your eyes. How many have I hidden? How 17 + 3 = 20 and 13 + 7 = 20 would be left if this number was cards as

20 – 3 = 17 and 20 – 17 = 13 taken away from 20 and record opposite do you know? What colour are they? How many

16 + 4 = 20 and 14 + 6 = 20 the subtraction. Repeat with at ; 20 bead were on the bottom row? What do you add to

20 – 4 =-16 and 20 – 16 = 4 least five different cards. strings seven to make ten?

Write 17 + = 20 on the whiteboard. What Ask children to close their eyes whilst Easier: Children use 20 beads ; 0-20 cards

you pick up a ‘slidy box’ card and hide strings to help. number goes in the box?

Write 20 - = 17 on the whiteboard. How What number is one of the numbers. Harder: Challenge children to

Repeat hiding write as many addition and many did I hide? So what number goes in the hiding? How do you know?

either of the first two numbers on related subtraction sentences box?

Repeat sliding other numbers of beads from addition cards, and either of the using pairs to 20 as they can. the bottom bar behind the whiteboard and second two numbers on subtraction encouraging children to use their pairs to ten cards. Ask children to explain how they to work out the missing number. know what the hidden number is.

Shuffle a pack of 0-20 cards. Take one. What

do I need to add to this number to make 20?15 + - = 20 Show this on the bead frame and record the

addition sentence. What if I took this number Easier: Use 20 bead strings to help.

away from 20? What would I be left with?

Show this on the bead frame and write the

subtraction. Repeat.

? Original teaching sequence copyright Hamilton Trust, who give permission for it to be adapted as wished by individual users. Y2 Maths TS3 – Spr – 3days

Write ? + ? = 10 on the board. There are two Children find at least two pairs of Group of 4-5 children ; Activity sheet

mystery numbers in number see resources) Show children this addition grid: (mystery numbers in this sentence. What could

sentences (see resources). They they be? If square is 8, what would triangle ? + 7 was 1? So there are lots of then make up two of their own for be? What if square

2 9 7 another pair to solve. possible answers.

Write 10 + ? + ? = 16 on the board. Easier: Most sentences have only 5 12 10 What could the mystery numbers be now? How one mystery number. How do you think it works? Discuss how much has been added on to 10 to 16? 7 and 2 make 9, and 7 and 5 make 12. Repeat with 8 + ? + ? = 16. Ask children to make some suggestions Repeat with 20 - ? - ? = 15. How much has about what the mystery number might taken away altogether? How do you know?be, and try out their ideas. Repeat with 10 - ? - ? = 5. Repeat with:

+ 10 6

3 13 9

? 12 8

Harder: Also try:

+ 10 ?

5 15 7

? 12 4

Write the following problem on the board: Children work in pairs to discuss, ; Activity sheet Group of 4-5 children

Sam collects toy tractors. He has 15! He has 5 and then solve simple word (see resources) Write the following story on the more for his birthday. problems. They use cubes or flipchart, using Post-its to denote space How many does he have now? sketches to help them where Go Maths Activity for numbers.

Ask children to read the problem in pairs. necessary. Book pages 36 and Jess collects soft toys. She has Where do you think he might keep his Easier: Some children may need 37 teddies and other soft toys.

adult support in reading, or work Altogether she has 20 soft toys. tractors? Do you have any toy tractors at

in mixed ability reading pairs. Read the number story through home? How could he find out how many

together and discuss what other soft tractors he’s got now? Will he have more or

Take suggestions, such as counting toys she might have. Do you think she fewer?

? Original teaching sequence copyright Hamilton Trust, who give permission for it to be adapted as wished by individual users. Y2 Maths TS3 – Spr – 3days

them all. He knows he’s got 15, so he doesn’t might have more teddies or other soft

need to count those, so he needs to work out toys? Do you have any at home? What

what number is 5 more than this. How could we do you have most of? How many has she

Ask children to suggest do this? Show 15 cubes and another 5 cubes. got altogether?

numbers to write on the Post-its? to Let’s pretend that these cubes are the

make the story true, i.e. numbers with a tractors he already has, and these five are the

total of 20. Take suggestions and use new ones. How many does he have altogether? Draw out counting on 5, or different Post-its? to put their How do you know?knowing that 15 and 5 makes 20. What number suggested numbers in to the story.

Repeat with: sentences could we write?

Display the following problem: Jess has 20 soft toys, too many to fit

Mum had ?20 for her birthday. She spent ?18 on her bed. She gives away to her on DVDs. How much does she have left? little sister. She has left.

Ask children to read it in pairs. I wonder what Easier: Jess has 10 soft toys.

Harder: Jess has 30 soft toys. DVDs she might have bought! Will she have more money now or less than when she

started? What do you think we need to do to

the numbers to solve it? What number

? Record 20 – 18. Do sentence could we write

That’s right, you know the answer? 2 what?

two pounds. Make a tower of 20 cubes, break

off 18. This is how much she spent, and this is how much she has left, not much! I wonder

Also what she might do with the two pounds. make two towers, one of 18 and one of 20, and

compare them to show the difference between

what she had and what she spent, reminding

children of how they found a difference last

term.