Mathematics
Grade 10
15 min
Repeating decimals
Repeating decimals
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1
Introduction & Learning Objectives
Learning Objectives
Define a repeating decimal and correctly identify its repetend.
Prove that any repeating decimal represents a rational number.
Convert a simple repeating decimal (e.g., 0.444...) into its equivalent fractional form using an algebraic method.
Convert a complex repeating decimal (e.g., 0.1232323...) into its equivalent fractional form.
Explain the logical sequence of steps required for the algebraic conversion process.
Distinguish between rational and irrational numbers based on their decimal expansions.
How can an infinitely long, repeating decimal be perfectly captured by a simple, finite fraction? 🤔 Let's use logic to unravel this mathematical magic!
In this tutorial, we will explore the logical connection between repeating decimals and rational n...
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Key Concepts & Vocabulary
TermDefinitionExample
Rational NumberAny number that can be expressed as a quotient or fraction p/q of two integers, where p is the numerator and q is the non-zero denominator.1/2, -5/3, 7 (which is 7/1), 0.25 (which is 1/4)
Repeating DecimalA decimal representation of a number whose digits are periodic and the infinitely repeated portion is not zero.1/3 = 0.333... or 1/7 = 0.142857142857...
RepetendThe sequence of digits that repeats infinitely in a repeating decimal.In 0.523523..., the repetend is '523'.
VinculumA horizontal line drawn over the repetend to indicate which digits repeat.0.3Ì… means 0.333... and 0.12Ì…4Ì…5Ì… means 0.12454545...
Terminating DecimalA decimal number that has a finite number of digits after the decimal point. All terminating decimals are rational numbers...
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Core Formulas
Conversion Rule for Simple Repeating Decimals
1. Let x = the repeating decimal. \n2. Multiply x by 10^k, where k is the number of digits in the repetend. \n3. Subtract the first equation from the second: (10^k)x - x. \n4. Solve for x.
Use this logical procedure when the repeating digits begin immediately after the decimal point. The goal is to create two equations where the decimal parts are identical, so they cancel out upon subtraction.
Conversion Rule for Complex Repeating Decimals
1. Let x = the decimal. \n2. Multiply x by 10^m to move the decimal past the non-repeating part. \n3. Multiply the new equation by 10^k, where k is the length of the repetend. \n4. Subtract the equation from step 2 from the equation in step 3. \n5. Solve for x.
Use this procedure when there are...
4 more steps in this tutorial
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Challenging
If a simple repeating decimal is represented as 0.ababab..., where 'a' and 'b' are distinct digits, what is its general fractional form?
A.ab/100
B.ab/99
C.(10a+b)/100
D.(10a+b)/99
Challenging
Which statement is true? Statement 1: 0.212121... > 7/33. Statement 2: 0.212121... < 7/33.
A.Statement 1 is true.
B.Statement 2 is true.
C.The two numbers are equal.
D.The relationship cannot be determined.
Challenging
Which statement best describes the logical necessity of the subtraction step in the algebraic conversion of a repeating decimal?
A.It simplifies the numerator of the resulting fraction.
B.It eliminates the infinite, repeating part of the decimal, transforming an infinite representation into a finite equation.
C.It determines the correct denominator for the fraction, which is always a power of 10.
D.It proves that the initial decimal was a non-terminating number.
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