Use the sliders to enter the denominators of your two fractions.[br][br]Now drag the YELLOW dot on the horizontal axis.[br][br]When the vertical coordinates of the WHITE dots are BOTH integers - [br]the horizontal coordinate of YELLOW dot is a common denominator of your two fractions[br][br][color=#ff0000][i][b]Why does this work?[br][br]What questions could/would you put to your students based on this applet?[/b][/i][/color]