SUBTRACTION YR Subtraction as ‘taking away’ from a group Practical or recorded using ICT (eg digital photos / pictures on IWB) Main methods used at Level 1: Practical or recorded using ICT. Pictures / Symbols (see above) L1 Pictures / Objects Symbols I have five cakes. I eat two of them. How many do I have left? Mum baked 9 biscuits. I ate 5. How many were left? Might be recorded as: 5–2=3 Taking away – jumps of 1 (modelled using bead strings) Criteria for Level 1 1a. Take 1 away from any number up to 10 and know what the answer is Know whether to subtract by recognising the word that is used in a problem 1b. Know all the names associated with adding or subtracting Take 1 away from any number and record the operation Take the smaller number from the larger when subtracting two unit numbers 1a. Work out whether to add or subtract when faced with a simple problem Know all subtraction bonds to 10 Counting on – jumps of 1 (modelled using bead strings) 13 – 5 = 8 11 – 8 = 3 -2 8 -1 -1 -1 -1 -1 -3 10 13 Criteria for level 2: 2c. Set out a subtraction on paper and take the larger number away from the smaller number Solve simple problems by working out which operation is needed Know addition and subtraction bonds to 10 2b. Subtract a 2 digit number from another 2 digit number using apparatus Use key words in problems to decide whether to subtract and then solve 2a. Subtract a 2 digit number from another 2 digit number without apparatus Use key words associated with numerical problems to help work out which operation to use 9 10 11 12 1 less (nos up to 10 ) (see recording) Counting on (efficient jumps) Subtraction facts to 10 TU – multiple of 10 Number line / no number line 1 / 10 less than a number 8 + 2 = 10 10 + 1 = 11 +1 +1 +1 No number line: 0 1 13 – 3 = 10 10 – 2 = 8 8 Mental Calculation [Might be recorded as: 9 – 5 = 4] Taking away (efficient jumps) 13 – 5 =8 Main methods used at Level 2: practical methods and expanded methods such as the use of the empty number line. Applying bods to 20 and 100. Level 2 Rapid Recall Recording AGE-RELATED EXPECTATIONS 2 3 4 5 6 7 8 9 10 11 13 Pictures / Symbols Partitioning Number lines – counting on 45 – 22 = 23 74 - 27 74 -27 = 47 +40 +3 74 – 20 = 54 54 – 4 = 50 50 – 3 = 47 Or 326 - 78 Number lines - taking away 74 -27 = 47 326 256 250 - 70 = 256 6 = 250 2 = 248 Subtraction facts to at least 10 0 27 30 [Also jumps can be in 10s and 1s] 70 Subtraction facts to 20 74 Differences of multiples of 10 Number line – counting on 141 - 89 = 52 +41 +11 [Also jumps can be in 10s and 1s] 89 Difference by counting up +4 100 141 Note the use of number bonds to 10/100 in order to use empty number line. TU – U / multiple of 10 Main methods used at level 3: empty number line, expanded decomposition and compact decomposition L3 Criteria for level 3: 3c. Confidently subtract 2 digit numbers from each other with no exchange Know the key words associated with subtraction and use them when solving problems 3b. Subtract any 2 digit number from another using decomposition when necessary Use rounding skills to estimate and check answers 3a. Subtract HTU/TU from HTU using decomposition Solve addition and subtraction problems requiring 2 steps Check if answer is reasonable Main methods used at level 4: compact decomposition (although strong mental strategies will ensure that children can make judgements about the best strategy) L4 L5 Criteria for L4 4c Subtract with thousands to 2 decimal places Use estimation to work out whether a calculation is likely to be correct Use subtraction to solve multi step problems involving whole numbers and decimals 4b Use a pencil and paper method confidently and accurately to solve ThHTU- ThHTU Find the difference between 2 decimal fractions with up to 3 digits and the same number of decimal places Solve multi step problems involving numbers in real life 4a Use a pencil and paper method confidently and accurately to solve subtraction problems involving any number of digits Check answers using the inverse operation Use subtraction to solve word problems involving numbers in real life Subtract 2 or more decimal fractions with up to 3 digits and either 1 or 2 decimal places 5c Consolidate efficient written methods of subtraction for whole numbers and decimal fractions Use checking procedures to check results Explain verbally how an answer is calculated Solve subtraction problems in a variety of contexts 5b subtract negative numbers in context appropriately use brackets in subtraction complete calculator and non calculator subtraction use approximate estimates subtraction using numbers to 100,000 Number lines – counting on Partitioning 754 – 186 = 568 + 500 Decomposition (compact method) 754 - 186 + 54 Derive differences of pairs of multiples of 10 / 100 / 1000 754 – 100 = 654 654 – 80 = 574 574 – 6 = 568 +14 754 TU – TU Decomposition (expanded) 723 – 458 = 265 [Red Alert] 700 400 20 50 Subtract pairs of multiples of 10 / 100 / 1000 3 8 (Th)HTU – (Th)HTU (small difference) 600 110 13 400 50 8 200 60 5 Number lines – counting on Partitioning 72.5 – 45.7 = 26.8 + 4.3 72.5 – 45.7 + 20 + 2.5 72.5 – 40 = 32.5 32.5 – 5 = 27.5 27.5 – 0.7 = 26.8 Decomposition 2362 – 548 = 1814 [Red Alert] 2000 300 500 60 40 1000 1300 500 800 50 12 40 8 10 4 1000 45.7 50 70 72.5 Note: this could primarily be used as a model for how decimals could be subtracted. Decomposition (compact method) 2 8 Use number facts for mental subtraction 9–2=7 0.9 – 0.2 = 0.7 0.09 – 0.02 = 0.07 Near multiple of 1000 – Near multiple of 1000 (eg 6070 – 4097) Decimal – Decimal (eg 9.5 – 3.7) Note: this is essentially a number line without the number line. Recognise when one method is more efficient. (See Y5 methods of recording) i.e when 8002 – 7998 = would not be best served by doing a formal decomposition HTU – HTU (by finding the difference) TU – near multiple of 10 (positive answers) Leads to 186 200 700 Vertical number line may be used to record calculation TU – U / TU There was 2.5 litres in the jug. Stuart drank 385 ml. How much was left? 18.07 km – 3.243 km (as above) Integer / decimal (1dp) – Integer / decimal (1dp) (In Y1: Subtraction as ‘taking away’ and ‘difference’ (by counting on) U–U TU – U (bridging 10) Y2 Subtraction as inverse of addition TU – TU (bridging 10s) Y4 HTU – TU HTU – HTU Decimals: money (£7.85 - £3.49) Y5 ThHTU – HTU Decimals up to 2dp (72.5 – 45.7) Y6 Consolidate / extend Y5 including: Decimal to 3 dp relating to measures