Mathematics
Grade 6
15 min
Subtract fractions with like denominators using number lines
Subtract fractions with like denominators using number lines
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1
Introduction & Learning Objectives
Learning Objectives
Identify fractions with like denominators.
Represent fractions on a number line.
Use a number line to model the subtraction of fractions with like denominators.
Accurately subtract fractions with like denominators.
Explain the process of subtracting fractions using a number line.
Write the difference of two fractions with like denominators.
Have you ever shared a pizza 🍕 and then someone ate a slice you were saving? How much of your share is left? Subtraction helps us figure that out!
In this lesson, you will learn how to subtract fractions that have the same bottom number, called like denominators. We'll use a visual tool called a number line to make this concept super clear and easy to understand. This skill is important for solving many real-wor...
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Key Concepts & Vocabulary
TermDefinitionExample
FractionA number that represents a part of a whole. It is written as a numerator over a denominator.In the fraction $\frac{3}{4}$, 3 is the numerator and 4 is the denominator.
NumeratorThe top number in a fraction, which tells you how many parts of the whole you have or are considering.In $\frac{5}{8}$, the numerator is 5, meaning you have 5 out of 8 equal parts.
DenominatorThe bottom number in a fraction, which tells you the total number of equal parts the whole is divided into.In $\frac{5}{8}$, the denominator is 8, meaning the whole is divided into 8 equal parts.
Like DenominatorsFractions that have the same denominator, meaning they are divided into the same number of equal parts.$\frac{3}{5}$ and $\frac{1}{5}$ have like denominators (both 5).
Number LineA straig...
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Core Formulas
Rule for Subtracting Fractions with Like Denominators
$\frac{a}{c} - \frac{b}{c} = \frac{a-b}{c}$
When subtracting fractions with the same denominator (c), you only subtract the numerators (a and b) and keep the denominator the same. The denominator tells you the size of the parts, and that size doesn't change when you take away some parts.
Representing Subtraction on a Number Line
To subtract $\frac{b}{c}$ from $\frac{a}{c}$ on a number line, first locate $\frac{a}{c}$. Then, move to the left (backwards) by 'b' unit fractions of size $\frac{1}{c}$.
The number line must be divided into 'c' equal parts between 0 and 1. Each mark represents a unit fraction. Starting at the first fraction, moving left by the number of parts indicated by the second fract...
5 more steps in this tutorial
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Challenging
The result of a subtraction problem is 4/11. If the number subtracted was 6/11, what was the original number (the starting point on the number line)?
A.2/11
B.10/11
C.6/11
D.4/11
Challenging
A student solves 9/10 - 5/10 and writes the answer 4/0. Using your knowledge of the number line model, what is the fundamental flaw in their thinking?
A.They think the size of the unit fractions (the denominator) changes when you subtract, which is incorrect as the number line's divisions stay the same.
B.They moved to the right on the number line instead of the left.
C.They counted the jumps incorrectly, moving 4 spaces instead of 5.
D.They set up the number line with 9 divisions instead of 10.
Challenging
In the general formula for subtraction on a number line, (a/c) - (b/c) = (a-b)/c, what does the letter 'b' represent in the context of the number line model?
A.The final landing position.
B.The total number of divisions on the number line.
C.The number of unit fraction jumps to the left.
D.The starting position on the number line.
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