CCSS.Math.Content.3.NF.A.2a
The standard
Represent a fraction 1/b on a number line diagram by defining the interval from 0 to 1 as the whole and partitioning it into b equal parts. Recognize that each part has size 1/b and that the endpoint of the part based at 0 locates the number 1/b on the number line.
Common Core State Standards for Mathematics
What this standard means
Students need to see a number line from 0 to 1 as one whole, then split that whole into equal parts. If the whole is cut into b equal parts, each part is 1/b. They also need to place 1/b at the first tick mark after 0, not inside the space or at 1.
Mastery looks like drawing a clean 0 to 1 number line, partitioning it evenly, labeling the first fraction correctly, and explaining why it is one equal part of the whole. Students often make unequal spaces, count tick marks instead of intervals, or think the denominator tells where to put the label without checking equal parts.
Ways to teach it
- Give pairs sentence strips labeled 0 and 1, have them fold into fourths or sixths, then mark and label 1/4 or 1/6.
- Ask students to explain in writing: Why is 1/5 located at the first tick mark after 0?
- Show three number lines for 1/3, only one partitioned correctly, and have students circle the correct one and explain.
- Connect to measuring cups by showing one whole cup divided into equal parts, then placing 1/4 on a taped number line.
Plan a lesson for CCSS.Math.Content.3.NF.A.2a
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Related standards
- CCSS.Math.Content.3.NF.A.1
Understand a fraction 1/b as the quantity formed by 1 part when a whole is partitioned into b equal parts; understand a fraction a/b as the quantity formed by a...
- CCSS.Math.Content.3.NF.A.2
Understand a fraction as a number on the number line; represent fractions on a number line diagram.
- CCSS.Math.Content.3.NF.A.2b
Represent a fraction a/b on a number line diagram by marking off a lengths 1/b from 0. Recognize that the resulting interval has size a/b and that its endpoint ...
- CCSS.Math.Content.4.NF.B.4a
Understand a fraction a/b as a multiple of 1/b.