Mathematics
Grade 7
15 min
Add and subtract fractions
Add and subtract fractions
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Identify common denominators in fractions.
Find the least common multiple (LCM) to determine the least common denominator (LCD) for two or more fractions.
Rewrite fractions as equivalent fractions with a common denominator.
Accurately add fractions with both like and unlike denominators.
Accurately subtract fractions with both like and unlike denominators.
Simplify fractional answers to their lowest terms.
Solve real-world problems involving the addition and subtraction of fractions.
Ever tried to share a pizza equally among friends, but some pieces were bigger than others? 🍕 How do you figure out how much pizza you ate in total if you had 1/4 of one and 1/8 of another?
In this lesson, you'll learn the essential skills to add and subtract fractio...
2
Key Concepts & Vocabulary
TermDefinitionExample
FractionA part of a whole, represented as a numerator over a denominator.In the fraction 3/4, it means 3 parts out of 4 total equal parts.
NumeratorThe top number in a fraction, indicating how many parts are being considered.In the fraction 2/5, the number 2 is the numerator.
DenominatorThe bottom number in a fraction, indicating the total number of equal parts the whole is divided into.In the fraction 2/5, the number 5 is the denominator.
Common DenominatorWhen two or more fractions have the same denominator.1/4 and 3/4 have a common denominator of 4.
Least Common Denominator (LCD)The smallest common multiple of the denominators of two or more fractions. It's the smallest number that all denominators can divide into evenly.For fractions 1/2 and 1/3, the LCD is...
3
Core Formulas
Adding Fractions with Like Denominators
$\frac{a}{c} + \frac{b}{c} = \frac{a+b}{c}$
To add fractions that already have the same denominator, simply add their numerators and keep the denominator the same. Always simplify your answer if possible.
Subtracting Fractions with Like Denominators
$\frac{a}{c} - \frac{b}{c} = \frac{a-b}{c}$
To subtract fractions that already have the same denominator, simply subtract their numerators and keep the denominator the same. Always simplify your answer if possible.
Adding/Subtracting Fractions with Unlike Denominators
To add or subtract fractions with unlike denominators, first find the Least Common Denominator (LCD). Then, rewrite each fraction as an equivalent fraction with the LCD. Finally, add or subtract the new numerators, keepi...
5 more steps in this tutorial
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Sign Up Free to ContinueSample Practice Questions
Challenging
A baker starts with a full bag of flour. He uses $\frac{1}{3}$ of the bag for a batch of cookies and $\frac{3}{8}$ of the bag for a cake. What fraction of the bag of flour is left?
A.\frac{17}{24}
B.\frac{7}{24}
C.\frac{4}{11}
D.\frac{1}{2}
Challenging
Find the missing fraction: $\frac{3}{5} + ? = \frac{7}{8}$
A.\frac{11}{40}
B.\frac{4}{3}
C.\frac{10}{13}
D.\frac{41}{40}
Challenging
A wooden plank is $10\frac{1}{2}$ feet long. A carpenter cuts off a piece that is $3\frac{2}{3}$ feet long. How long is the remaining piece of the plank?
A.7\frac{1}{6}
B.7\frac{1}{5}
C.6\frac{1}{6}
D.6\frac{5}{6}
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