Why a number line, and why past 1?

"Where does 5/4 go?" is a different question than "shade 5/4 of a pizza," and it's the more powerful one. Placing a fraction on a number line trains kids to treat it as one number with a size, not two whole numbers stacked on top of each other. That's whole-number bias: 1/8 looks bigger than 1/4 to a lot of kids because 8 beats 4, and it's one of the most stubborn errors in elementary math. This tool defaults to lines that run past 1, because fractions greater than a whole are the fastest way out of the "a fraction is a slice of one pizza" trap. Flash a fraction, let the class argue about where it lives, then reveal the partitions and count the unit fractions together.