Mathematics
Grade 5
15 min
Add mixed numbers with unlike denominators
Add mixed numbers with unlike denominators
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Introduction & Learning Objectives
Learning Objectives
Identify the whole number and fractional parts of a mixed number.
Find the least common denominator (LCD) for two fractions with unlike denominators.
Convert fractions to equivalent fractions with a common denominator.
Add the whole number parts and the fractional parts of mixed numbers separately.
Convert an improper fraction sum back into a mixed number.
Simplify the fractional part of a mixed number sum to its lowest terms.
Solve real-world problems involving the addition of mixed numbers with unlike denominators.
Ever tried to combine two different amounts of ingredients, like 1 1/2 cups of flour and 2 3/4 cups of sugar? 🍰 How much do you have in total?
In this lesson, you'll learn how to add mixed numbers even when their fraction parts have...
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Key Concepts & Vocabulary
TermDefinitionExample
Mixed NumberA number that combines a whole number and a fraction.3 1/2 (three and a half), where 3 is the whole number and 1/2 is the fraction.
FractionA number that represents a part of a whole. It has a numerator (top number) and a denominator (bottom number).The fraction 2/3 means 2 parts out of 3 equal parts.
NumeratorThe top number in a fraction, showing how many parts of the whole are being considered.In the fraction 3/4, the numerator is 3.
DenominatorThe bottom number in a fraction, showing the total number of equal parts that make up the whole.In the fraction 3/4, the denominator is 4.
Unlike DenominatorsFractions that have different numbers in their denominators.1/2 and 3/4 have unlike denominators (2 and 4).
Common DenominatorA shared multiple of the denom...
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Core Formulas
Finding a Common Denominator
To add fractions with unlike denominators, you must first find a common denominator. The most efficient common denominator is the Least Common Multiple (LCM) of the original denominators.
When you have two fractions $\frac{a}{b}$ and $\frac{c}{d}$ with $b \neq d$, you need to find a common multiple of $b$ and $d$. Let $L = \text{LCM}(b, d)$. Then, convert each fraction to an equivalent fraction with $L$ as the new denominator: $\frac{a}{b} = \frac{a \cdot (L/b)}{b \cdot (L/b)}$ and $\frac{c}{d} = \frac{c \cdot (L/d)}{d \cdot (L/d)}$.
Adding Mixed Numbers (Separate Parts Method)
To add two mixed numbers $(W_1 + \frac{N_1}{D_1})$ and $(W_2 + \frac{N_2}{D_2})$: 1. Add the whole number parts: $W_1 + W_2$. 2. Add the fractional parts after finding a com...
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Challenging
A triangle has three sides. The first side is $2 \frac{1}{2}$ inches long. The second side is $3 \frac{1}{4}$ inches long. The third side is $1 \frac{5}{8}$ inches long. What is the perimeter of the triangle?
A.7 \frac{3}{8} inches
B.6 \frac{7}{14} inches
C.6 \frac{7}{8} inches
D.7 \frac{3}{4} inches
Challenging
The sum of two mixed numbers is $7 \frac{1}{12}$. If one of the mixed numbers is $4 \frac{2}{3}$, what is the other mixed number?
A.3 \frac{5}{12}
B.2 \frac{7}{12}
C.2 \frac{5}{12}
D.3 \frac{1}{9}
Challenging
Compare the following two sums. Which statement is true?
Sum 1: $2 \frac{1}{2} + 3 \frac{1}{3}$
Sum 2: $1 \frac{3}{4} + 4 \frac{1}{6}$
A.Sum 1 is greater than Sum 2
B.Sum 1 is equal to Sum 2
C.Sum 2 is greater than Sum 1
D.It is impossible to compare them
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