Every line runs from 0 to 1, divided into equal parts - thirds, quarters, fifths, sixths, eighths or tenths - with every tick labelled as a fraction. An arrow sits over one of them, and the question is which fraction that is.
This is where a fraction stops being a piece of a pizza and becomes a number with a place. A student who can shade three quarters of a circle but cannot find 3/4 on a line has the first idea and not the second, and the second is the one the rest of fractions is built on.
Because it is what makes a fraction a number rather than a shape. Once 3/4 has a position, comparing it to 2/3 is looking at which is further right, and adding fractions is moving along a line.
Thirds, quarters, fifths, sixths, eighths and tenths. Halves are left out - a line with one tick in the middle does not give a student much to read.
No. On a line divided into sixths, the third tick is written 3/6, because that is the tick it is. Simplifying is a different question and our simplifying fractions worksheets ask it.
Third grade - it is Common Core 3.NF.A.2 almost exactly - and it comes back whenever comparing or equivalent fractions are taught.