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Repeating decimals

Repeating decimals

Repeating decimals are decimal numbers in which one or more digits repeat infinitely. For example, the fraction 13\frac{1}{3} equals 0.333...0.333..., where the digit "3" continues indefinitely.

These decimals can be denoted using a bar over the repeating digit(s) (e.g., 0.30.\overline{3}). Repeating decimals arise from rational numbers, which are ratios of integers. Not every decimal is repeating; some are terminating (like 0.250.25), while others are non-repeating and infinite (like π\pi or ee).

In summary, repeating decimals provide a way to express certain fractions in decimal form, exhibiting periodicity in their digit sequences.

Part 1: Converting a fraction to a repeating decimal

To convert a fraction like 19/27 into a decimal, you should divide 27 into 19, and use the remainder to figure out the decimal. The decimal begins 0.703703..., and the notation for a repeating decimal like this is to write the numbers that repeat and then put a line above them. The first six digits of the decimal should be included in the answer.

When studying "Converting a fraction to a repeating decimal," focus on these key points:

  1. Understanding Fractions: Recognize that a fraction consists of a numerator (top number) and a denominator (bottom number).

  2. Long Division: Use long division to divide the numerator by the denominator. This is the main method for converting fractions to decimals.

  3. Identifying Repeats: If the long division process produces a remainder that has already occurred, the decimal will begin to repeat. Document the sequence of remainders to spot this.

  4. Repeating Decimal Notation: Use notation such as a bar (e.g., 0.3̅) to indicate the repeating part of the decimal.

  5. Terminating vs. Repeating: Understand the difference between fractions that yield terminating decimals (exact decimals that end) and those that yield repeating decimals.

  6. Prime Factorization: Know that a fraction will have a terminating decimal if, after simplification, its denominator contains only the prime factors 2 and/or 5.

  7. Converting Back: Be able to convert a repeating decimal back into a fraction if needed by setting up an equation and solving for the variable.

By mastering these points, you'll be well-equipped to convert fractions into repeating decimals.

Part 2: Converting repeating decimals to fractions (part 1 of 2)

The process of converting a repeating decimal to a fraction can be broken down into a few easy steps. To start, set the decimal equal to a variable. Multiply the decimal by 10 and subtract the original decimal from it. Finally, divide both sides by 9 to obtain the fractional form of the decimal. For example, 0.7 repeating would be 7/9, and 1.2 repeating would be 11/9.

Here are the key points for converting repeating decimals to fractions:

  1. Understanding Repeating Decimals: Recognize that a repeating decimal has a digit or group of digits that repeat indefinitely (e.g., 0.333... or 0.142857142857...).

  2. Identifying the Decimal: Clearly identify the repeating part of the decimal. For example, in 0.666..., "6" is the repeating digit.

  3. Setting Up an Equation: Let the repeating decimal be equal to a variable (e.g., let x=0.666...x = 0.666...).

  4. Multiplying to Eliminate the Decimal: Multiply the variable by a power of 10 that matches the number of repeating digits. For 0.666..., multiply by 10 to get 10x=6.666...10x = 6.666....

  5. Subtracting the Original Equation: Subtract the original equation from this new equation to eliminate the repeating part. For example:

    10xx=6.666...0.666...10x - x = 6.666... - 0.666...

    This simplifies to 9x=69x = 6.

  6. Solving for the Variable: Solve for xx. Continuing from the previous step, divide both sides by 9:

    x=69x = \frac{6}{9}
  7. Simplifying the Fraction: Simplify the fraction to its lowest terms. In this case, 69\frac{6}{9} simplifies to 23\frac{2}{3}.

  8. Result Verification: Optionally, convert the fraction back to a decimal to confirm the result matches the original repeating decimal.

By following these steps, you can convert any repeating decimal into a fraction accurately.

Part 3: Converting repeating decimals to fractions (part 2 of 2)

Repeated decimals can be converted into fractions by shifting the decimal to the right and subtracting the decimals. To do this, multiply the number by 10 to the second power, then subtract. For example, 0.363636 repeating is 4/11 and 0.7141414 repeating is 707/990. Another example is 3.257257257 repeating, which is 3257/999. This calculation can be done in the head or by borrowing. After the subtraction, the numerator and denominator can be reduced and the fraction can be simplified.

Sure! Here are the key points to learn when studying "Converting repeating decimals to fractions (part 2 of 2)":

  1. Setup of the Equation: When converting a repeating decimal to a fraction, start by letting the repeating decimal equal a variable (e.g., x=0.666...x = 0.666...).

  2. Multiply to Shift Decimal: Multiply both sides of the equation by a power of 10 that matches the length of the repeating segment (e.g., for 0.666..., multiply by 10 to get 10x=6.666...10x = 6.666...).

  3. Subtract the Original Equation: Set up a subtraction between the two equations (the original and the multiplied version). This helps eliminate the repeating part (e.g., 10xx10x - x).

  4. Solve for xx: Simplify the resulting equation to solve for the variable. This will give you a numeric result (e.g., 9x=69x = 6, thus x=69x = \frac{6}{9}).

  5. Reduce the Fraction: Reduce the resulting fraction to its simplest form (e.g., 69=23\frac{6}{9} = \frac{2}{3}).

  6. Use of Mixed Numbers: If the repeating decimal is a mixed number (e.g., 2.342.3\overline{4}), convert the whole number separately and combine it with the fraction derived from the decimal part.

  7. Special Cases: Be aware of any special cases, such as terminating decimals or non-repeating parts, and how they affect the conversion.

By following these steps, you can effectively convert any repeating decimal into a fraction.