Suitable for self learning or classroom lesson presentation.
Updated 11 Aug 2014. Minor bug in mixed number fraction display.
Updated 17 Mar 2019 Use of button to step through addition & subtraction process, and use inputboxes for numerators and denominators
See John Ulbright's work at https://www.geogebra.org/material/show/id/szwBQ7wa
(which uses bar diagrams to represent fractions)
See also https://www.geogebra.org/material/show/id/qwjhd8kx
on comparing fractions by converting to equivalent fractions using common denominators or common numerators!
