Enlighten me about number bonds

[MrsFogi]

I need to work on dd's number bonds to 20. Does this mean 1+19 = 20, 2+ 18 = 20, 3+17=20 etc or all possible additions that equal a number up to 20? Either way, how do I go about helping dd learn these. Also, is the aim that she can do the answers without a thought? Thanks

Yes, it does mean those and also yes, it does mean answer without a thought. We had fish with spots on each side at the school I worked in. You get the child to pull one out of a bag and look at the spots on one side and see if they can work out what will be on the other side.