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Activity 3

Use number facts to add and subtract 1-digit numbers to/from 2-digit numbers

 

Look at these calculations together :-

10 - 2      46 + 3      7 +8      64 - 2     4 + 2      15 + 3     10 + 10     9 - 1    13 - 7

19 + 7      70 + 8    23 - 3     63 + 2     3 + 7       76 - 4

 

Ask your child to pick out the sum that ʻjust knowʼ the answer to (i.e. know off by heart) and those they need to work out.

Point out that 70 + 8 is easier than 7 + 8 even though the numbers are bigger. Sometimes a calculation is one we just know even though it has big numbers.

 

Ask your child to write or tell you 10 additions that they confidently know e.g. 10 +10; 5 +5; 4+2; 20 +2 etc. Were they correct? Check the answers together. 

 

Now ask them to give you 10 additions they don’t know the answers to e.g. 7 + 8; 6 + 9

Ensure they keep the answers to within 100.

 

How can you work the answers out together? 

Try adding the 10’s numbers together, then the 1’s numbers together and finally adding both numbers together. 

Are there any patterns? Doubles? Can you round up or down to the nearest 10 to help you?

Crack the Code - Worksheet

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