My 4yo daughter seems to have grasped the fact that half of ten is five. And she seems to have grasped the fact that twice ten is twenty. And now appears to be chucking facts around like this means I have five, mum has five, dad has five and the baby has five. I'm fairly sure this is coincidence and is just because we've talked about fives and tens before. But I'm also pretty sure that I didn't chuck around mental arithmetic like it was confetti when I was four. I'd like to encourage her to do this but it's spontaneous. And I can't quite see how one extends spontaneity. Can one? Or does one just let it be?