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Question

Give the expression of   \(8.\overline{48}\)

The correct answer is \(\frac{840}{99}\)

Expressing Repeating Decimals as Fractions

We are asked to express the repeating decimal \(8.\overline{48}\) as a fraction. A repeating decimal is a decimal in which one or more digits repeat infinitely.

To convert a repeating decimal into a fraction, we can follow these steps:

  1. Let the given decimal be equal to a variable, say \(x\).

    So, let \(x = 8.\overline{48}\)

    This means \(x = 8.484848...\) (Equation 1)

  2. Identify the number of repeating digits. In \(8.\overline{48}\), the repeating digits are '48', which is a block of 2 digits.

  3. Multiply the equation by \(10^n\), where \(n\) is the number of repeating digits. Since there are 2 repeating digits, we multiply by \(10^2 = 100\).

    \(100x = 100 \times 8.484848...\)

    \(100x = 848.484848...\) (Equation 2)

  4. Subtract Equation 1 from Equation 2. This step eliminates the repeating part of the decimal.

    \(100x - x = 848.484848... - 8.484848...\)

    \(99x = 840\)

  5. Solve for \(x\) by dividing both sides by the coefficient of \(x\).

    \(x = \frac{840}{99}\)

  6. Simplify the fraction if possible. In this case, both 840 and 99 are divisible by 3 (since the sum of digits of 840 is 8+4+0=12, divisible by 3; the sum of digits of 99 is 9+9=18, divisible by 3).

    \(x = \frac{840 \div 3}{99 \div 3} = \frac{280}{33}\)

The simplified fraction is \(\frac{280}{33}\). However, the options provided are not in simplified form. Let's check the options against the unsimplified fraction \(\frac{840}{99}\).

Comparing \(\frac{840}{99}\) with the given options:

  • Option 1: \(\frac{169.6}{20}\). This is not a simple fraction. Converting it to a simple fraction: \(\frac{169.6 \times 10}{20 \times 10} = \frac{1696}{200} = \frac{212}{25}\). This is not \(\frac{840}{99}\).
  • Option 2: \(\frac{840}{99}\). This matches our result before simplification.
  • Option 3: \(\frac{848}{100}\). This represents \(8.48\), not \(8.\overline{48}\).
  • Option 4: \(\frac{848}{99}\). This would represent a different repeating decimal.

Therefore, the expression of \(8.\overline{48}\) as a fraction among the given options is \(\frac{840}{99}\).

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Important Questions from Rational or Irrational Numbers

  1. Which of the following number is irrational?

  2. Which of the following numbers will have an irrational square root?

  3. What is the square root of 16 + 6√7?

  4. A non-terminating but recurring decimal is:

  5. Which of the following statements is true?

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