Addition of fractions (pieadd)

This applet allows students to understand the addition of two fraction numbers, and the relationship between numerator and denominator in a fraction.the sliders m and b controls the amount number for the numerators.While the sliders n and a control the denominators. All the three pies work perfectly when the fractions are less than one. However, if the result is more than one, this applet can not compute the fractions.