It helps you find pairs of numbers that add up to \(10\). Knowing these pairs makes adding other numbers, especially when you have to cross ten, much easier.
What number do you add to \(1\) to make \(10\)?
$$ 1 + 9 = 10 $$
What number do you add to \(2\) to make \(10\)?
$$ 2 + 8 = 10 $$
What number do you add to \(3\) to make \(10\)?
$$ 3 + 7 = 10 $$
What number do you add to \(4\) to make \(10\)?
$$ 4 + 6 = 10 $$
What number do you add to \(5\) to make \(10\)?
$$ 5 + 5 = 10 $$
I have \(6\). How many more do I need to make \(10\)?
You need \(4\) more. \(6 + 4 = 10\).
I have \(7\). How many more do I need to make \(10\)?
You need \(3\) more. \(7 + 3 = 10\).
I have \(8\). How many more do I need to make \(10\)?
You need \(2\) more. \(8 + 2 = 10\).
I have \(9\). How many more do I need to make \(10\)?
