Adding or Subtracting Fractions with Like Denominators on a Number Line
Grade 4 Eureka Math students add and subtract fractions with like denominators directly on a number line by treating fraction marks as unit steps. For addition, partition the line by the denominator, start at the first fraction, and move right the number of steps equal to the second numerator. For subtraction, move left. To add 4/6 + 3/6, start at 4/6 and move 3 units right to land on 7/6. To subtract 5/4 minus 2/4, start at 5/4 and move 2 units left to 3/4. This model makes fraction operations visible and concrete.
Key Concepts
To add or subtract fractions with like units on a number line, first partition the line according to the denominator. For addition, start at the first fraction and move to the right (forward). For subtraction, start at the first fraction and move to the left (backward).
Common Questions
How do you add fractions on a number line?
Partition the number line into equal sections matching the denominator. Start at the first fraction and count right by the second fraction's numerator.
How do you solve 4/6 + 3/6 on a number line?
Mark the line in sixths. Start at 4/6 and move 3 units right to land on 7/6.
How do you subtract fractions on a number line?
Start at the minuend fraction and move left by the subtrahend's numerator. The landing point is the difference.
What does the denominator tell you when setting up the number line?
The denominator tells you how many equal parts to divide each whole into. Each segment represents one unit fraction.
Why is the number line a good model for fraction operations?
It shows fractions as positions and operations as movement, making abstract addition and subtraction physically meaningful.