Subtract 11 or 21

practice at subtracting 11 or 21 from 2-digit numbers 'in your head'.

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Sometimes it's easier to do subtraction by counting up, especially if the numbers are close to each other.

Subtracting 2-digit numbers, but no 'decomposition' needed. A good mental arithmetic exercise.

Using mental methods to subtract 19 from 2-digit numbers.

Use counting up to find differences between numbers either side of 100.

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