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Ways to add and subtract

Ways to add and subtract. December 2011. Kindly contributed by Kate Lindley Search for Kate on www.skillsworkshop.org Visit the download page for this resource to find further curriculum links and related resources.

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Ways to add and subtract

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  1. Ways to add and subtract December 2011. Kindly contributed by Kate Lindley Search for Kate on www.skillsworkshop.org Visit the download page for this resource to find further curriculum links and related resources. Note: some screens adapted from BBC Skillswisehttp://www.bbc.co.uk/skillswise/maths Curriculum links For underpinning the following Functional Maths coverage & range statements: Entry 2 Understand and use addition/subtraction in practical situations Entry 3 Add and subtract using three-digit numbers Adult Numeracy: N1/E2.3 Add and subtract two-digit whole numbers N1/E3.2 Add and subtract using three-digit whole numbers

  2. Ways to add and subtract Number lines, rounding and splitting

  3. Number line for counting on When you have pictured that line, count on from 37 to 40, which makes 3. Keep that 3 in your head. Then, count from 40 to 50, which is 10. Now all you need to do is add the 3 to the 10. This makes 13. So: The difference between 37 and 50 is 13.Or 50 - 37 = 13 Use this method to find the difference between 37 and 50. This is the same as the sum 50 - 37.

  4. Rounding - Addition Imagine you are in a shop and you have to quickly work out an amount. £3.70 + £1.00 = £4.70. Taking away 10p gives £4.60 Have a look at how this addition sum can be solved with rounding:75 + 19 First, round the 19 up to 20 and work out the sum:75 + 20 = 95 Because 20 is 1 more than 19, you then need to subtract 1 from the total.95 - 1 = 94 Then you can see that:75 + 19 = 94

  5. Rounding - Subtraction Imagine you are in a shop and you have to quickly work out an amount. £3.70 - £1.00 = £2.70. Adding 10p gives £2.80. Have a look at how this subtraction sum can be solved with rounding:64 - 17 First, round the 17 up to 20 and work out the sum:64 - 20 = 44 Because 20 is 3 more than 17, you have taken 3 too many from the total. You need to add 3: 44 + 3 = 47 So you can see that:64 - 17 = 47

  6. Rounding down - Addition & Subtraction We don’t always round up to the nearest 10 or 100. We can round down too. For example: £4.60 – 62p 62p is a little bit more than 60p. I’ll take away 60p then take away 2p more. £4.60 – 60p = £4.00. Taking away 2p gives £3.98 Have a look at how this addition sum can be solved with rounding down:75 + 13 First, round the 13 down to 10 and work out the sum:75 + 10 = 85 Because 13 is 3 more than 10, you then need to add 3 to the total.85 + 3 = 88 Then you can see that:75 + 13= 88

  7. Splitting up numbers - Addition Take a look at this addition sum:80 + 49 To make it easier, split the 49 into 40 + 9. This makes the sum:80 + 40 + 9 = First, add the first two numbers:80 + 40 = 120 Then add the result of that sum to the third number to get the answer:120 + 9 = 129

  8. Splitting up numbers - Subtraction Take a look at this subtraction sum:150 - 34 To make it easier, split the - 34 into - 30 - 4. This makes the sum:150 - 30 – 4 First, subtract the 30 from 150:150 - 30 = 120 Then, subtract the 4 from the 120 to get the answer:120 - 4 = 116

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