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Published byMarcus Ross Lynch Modified over 7 years ago

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Today we will be learning to work out answers to calculations by using: what we already know about addition and subtraction patterns of similar calculations.

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Mental Activity We are going to practise adding and subtracting numbers up to 20.

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What number do you need to add to each card to make 20?

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911

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128

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713

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164

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155

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317

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You have to make 12. Work in a group. Take a number card from 0 to 20. Choose a partner with a number that you can add or subtract from your number to make 12.

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I have 8 My partner has 4 8 + 4 = 12 Example:

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Now find a partner to make 15. Now find a partner to make 16. Now find a partner to make 18. Now find a partner to make 19.

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Main Activity Today we will use what we already know to help us to work out other number facts.

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70 + 70 = What do we already know that could help us to work this out?

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70 + 70 = Double 7 = 14 70 is ten times bigger than 7 Double 70 will be ten times bigger than 14 140 Double 70 = 140

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Let’s try some more… Can you say the easy double fact you use to find the answer? Addition Double fact 60 + 60 =120 40 + 40 =80 6 + 6 =12 4 + 4 = 8 80 + 80 =160 8 + 8 = 16

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Work with a partner. Double all the multiples of 10 to 100. 100 90 80 70 60 50 40 30 20 10 DoubleNumber 20 40 60 80 100 120 140 160 180 200

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What number knowledge would you use to work out this calculation? 8 + 4 = 12 so 80 + 40 = 120 80 + 40 =

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Group Work Adding and subtracting work Work on number chains

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