Mathematics
Grade 8
15 min
Multiply and divide rational numbers
Multiply and divide rational numbers
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define rational numbers and identify their components.
Multiply two or more rational numbers, including fractions, decimals, and mixed numbers.
Divide two rational numbers, including fractions, decimals, and mixed numbers.
Correctly apply the rules of signs for multiplication and division of rational numbers.
Simplify rational expressions involving multiplication and division to their lowest terms.
Solve real-world problems that require multiplying and dividing rational numbers.
Ever wonder how chefs adjust recipes for different serving sizes, or how engineers calculate material needs for a fraction of a project? 🧑🍳📐 It all involves multiplying and dividing parts of numbers!
In this lesson, you'll learn the essential rules and techniques for mul...
2
Key Concepts & Vocabulary
TermDefinitionExample
Rational NumberA number that can be expressed as a fraction $\frac{p}{q}$ where $p$ and $q$ are integers and $q$ is not zero. This includes integers, fractions, and terminating or repeating decimals.$\frac{3}{4}$, $-5$, $0.25$ (which is $\frac{1}{4}$), $1.\overline{3}$ (which is $\frac{4}{3}$)
NumeratorThe top number in a fraction, representing the number of parts being considered.In the fraction $\frac{5}{8}$, the numerator is $5$.
DenominatorThe bottom number in a fraction, representing the total number of equal parts into which the whole is divided.In the fraction $\frac{5}{8}$, the denominator is $8$.
ReciprocalThe number by which another number must be multiplied to produce $1$. For a fraction $\frac{a}{b}$, its reciprocal is $\frac{b}{a}$.The reciprocal of $\fr...
3
Core Formulas
Multiplication of Rational Numbers (Fractions)
$\frac{a}{b} \cdot \frac{c}{d} = \frac{a \cdot c}{b \cdot d}$
To multiply two fractions, multiply their numerators to get the new numerator, and multiply their denominators to get the new denominator. Always simplify the resulting fraction if possible.
Division of Rational Numbers (Fractions)
$\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \cdot \frac{d}{c}$
To divide by a fraction, multiply the first fraction by the reciprocal of the second fraction (the divisor). Then follow the rules for multiplication.
Rules of Signs for Multiplication and Division
$\text{Positive} \times \text{Positive} = \text{Positive}$ \newline $\text{Negative} \times \text{Negative} = \text{Positive}$ \newline $\text{Positive} \times \text{Negative} =...
5 more steps in this tutorial
Sign up free to access the complete tutorial with worked examples and practice.
Sign Up Free to ContinueSample Practice Questions
Easy
According to the tutorial's definition, which of the following is the best description of a rational number?
A.Any number that is not a whole number.
B.Only positive and negative fractions.
C.Only terminating decimals.
D.number that can be expressed as a fraction p/q, where p and q are integers and q is not zero.
Easy
What is the product of 2/3 and 4/5?
A.8/15
B.6/20
C.10/12
D.8/8
Easy
What is the reciprocal of the rational number -9?
A.9
B.-1/9
C.1/9
D.0
Want to practice and check your answers?
Sign up to access all questions with instant feedback, explanations, and progress tracking.
Start Practicing Free