perhaps we should revert to the historical vertical line instead of a point (that way at least you might see some trace of it in student's work) to mark the border between wholes and deci-parts of wholes
three interesting questions for discussion are:
- what is 4.6 + 3?
- what is half way between 3.1 and 3.2?
- what is 1 - 0.4?
hidden noughts and decimal points are sometimes helpful (pointers)...
"can you see the hidden decimal point after the 3?"
"well that's because it isn't there, but it is kind of isn't it?"