Question

How does $4.30 relate 4.3

Answer 1

These both represent the same number.
In $4.30 or just 4.30, the zero does not have any number after it, so it doesn't need to be there as a placeholder. When you take away the zero, it's just 4.3.

Answer 2

JE NE SAIS PAS COMMENT ON VA FAIRE POUR ALLER À LONDRES