Mathematics
Grade 9
15 min
Select the correct decimal
Select the correct decimal
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define a rational expression and its decimal forms.
Convert a rational number (fraction) into its decimal equivalent using long division.
Identify the difference between a terminating and a repeating decimal.
Use bar notation correctly to represent repeating decimals.
Analyze the prime factors of a denominator to predict whether a rational number's decimal form will terminate or repeat.
Evaluate a simple rational expression for a given value and convert the resulting fraction to a decimal.
Have you ever noticed that 1/4 of a dollar is $0.25 (it ends), but 1/3 of a dollar is $0.333... (it goes on forever)? 🤔 Let's find out why!
This tutorial will teach you how to convert rational expressions, which are essentially fractions with polynomials, in...
2
Key Concepts & Vocabulary
TermDefinitionExample
Rational ExpressionA fraction in which the numerator and the denominator are polynomials. For our purposes, we will start with the simplest rational expressions: rational numbers.Simple: `3/4`. Algebraic: `(x + 2) / (x - 1)`.
Terminating DecimalA decimal number that has a finite number of digits after the decimal point. It ends.`3/8 = 0.375`
Repeating DecimalA decimal number that has a digit or a block of digits that repeat infinitely after the decimal point.`2/11 = 0.181818...`
Bar Notation (Vinculum)A horizontal line placed over the repeating digit or block of digits in a repeating decimal.`0.181818...` is written as `0.\overline{18}`.
Prime FactorizationThe process of breaking down a number into its prime number factors.The prime factorization of 12 is `2 x 2 x 3`...
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Core Formulas
Fraction to Decimal Conversion
To convert a rational number `p/q` to a decimal, perform the division `p ÷ q`.
This is the fundamental method for finding the decimal representation of any fraction. The numerator is the dividend and the denominator is the divisor.
Terminating Decimal Rule
A rational number `p/q`, in its simplest form, will be a terminating decimal if the prime factorization of the denominator `q` consists ONLY of 2s and/or 5s. Formula: `q = 2^a \cdot 5^b` where `a` and `b` are non-negative integers.
Use this rule to quickly predict if a decimal will end without doing the full division. First, simplify the fraction, then find the prime factors of the denominator.
Repeating Decimal Rule
A rational number `p/q`, in its simplest form, will be a repeating dec...
5 more steps in this tutorial
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Challenging
Consider the expression (x + 1) / (x + 4). For which integer value of x from the set {1, 2, 3, 4} will the expression evaluate to a fraction that becomes a repeating decimal?
A.x = 1
B.x = 2
C.x = 3
D.x = 4
Challenging
If p/q is a simplified rational number where the denominator q = 2ᵃ * 3ᵇ * 5ᶜ, and a, b, and c are non-negative integers, under which specific condition will the decimal representation of p/q ALWAYS terminate?
A.If b = 0
B.If a > 0 and c > 0
C.If b > 0
D.If a = c
Challenging
Evaluate the expression (10 - 2x) / (3x) for x = 4. Then, select the correct decimal representation.
A.0.1$\overline{6}$
B.0.25
C.0.16
D.0.$\overline{16}$
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