The Mathematics Academy regularly publishes interactive GeoGebra applets that allow a student to make changes and see the effect. The latest one is a number line from 0 to 1, which shows a fraction on the number line. Students can change the numerator or the denominator and see how the location of the fraction is affected.
I would accompany this activity with a set of questions for students to answer, leading them to make conjectures about fractions. I would like to see the number line extend beyond 1, but this is still a great way for students to visualize fractions in the way that they are introduced in Grade 3 in the Common Core…as units on a number line. By increasing (or decreasing) the numerator by one, students can see the fraction “marching” up (or down) the number in equal steps (distances). By increasing the denominator, students can see the fraction stay on the same “step”, but can see the number of steps between 0 and 1 increase, resulting in smaller steps. The result is a smaller fraction closer to zero. They see the opposite effect when they decrease the denominator. The fraction stays on the same “step”, but the steps become larger, causing the fraction to move to the right away from zero closer to one.
Here is the link: