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Question

Simplify the following expression.

\(\frac{{6\frac{1}{2} + 2\frac{5}{7} \times \frac{{14}}{{19}} - \frac{1}{2} \div 2\ of\frac{1}{4}}}{{11 \times 12 \div 12 + 12}}\)

The correct answer is \(\frac{{15}}{{46}}\)

Simplifying Complex Mathematical Expressions

To simplify the given complex fraction, we need to evaluate the numerator and the denominator separately following the order of operations (BODMAS/PEDMAS).

Understanding the Order of Operations (BODMAS)

BODMAS stands for:

  • Brackets (or Parentheses)
  • Orders (powers, square roots, etc.) / Of
  • Division and Multiplication (from left to right)
  • Addition and Subtraction (from left to right)

The expression is:

\(\frac{{6\frac{1}{2} + 2\frac{5}{7} \times \frac{{14}}{{19}} - \frac{1}{2} \div 2\ of\frac{1}{4}}}{{11 \times 12 \div 12 + 12}}\)

Simplifying the Numerator

Let's evaluate the numerator first: \(6\frac{1}{2} + 2\frac{5}{7} \times \frac{{14}}{{19}} - \frac{1}{2} \div 2\ of\frac{1}{4}\)

First, convert the mixed numbers to improper fractions:

  • \(6\frac{1}{2} = \frac{(6 \times 2) + 1}{2} = \frac{12 + 1}{2} = \frac{13}{2}\)
  • \(2\frac{5}{7} = \frac{(2 \times 7) + 5}{7} = \frac{14 + 5}{7} = \frac{19}{7}\)

The numerator becomes: \(\frac{13}{2} + \frac{19}{7} \times \frac{14}{19} - \frac{1}{2} \div 2\ of\frac{1}{4}\)

Next, evaluate the 'of' operation:

  • \(2\ of\frac{1}{4} = 2 \times \frac{1}{4} = \frac{2}{4} = \frac{1}{2}\)

The numerator becomes: \(\frac{13}{2} + \frac{19}{7} \times \frac{14}{19} - \frac{1}{2} \div \frac{1}{2}\)

Now, perform multiplication and division from left to right:

  • Multiplication: \(\frac{19}{7} \times \frac{14}{19} = \frac{\cancel{19}}{7} \times \frac{2 \times 7}{\cancel{19}} = \frac{2 \times \cancel{7}}{\cancel{7}} = 2\)
  • Division: \(\frac{1}{2} \div \frac{1}{2} = \frac{1}{2} \times \frac{2}{1} = 1\)

The numerator becomes: \(\frac{13}{2} + 2 - 1\)

Finally, perform addition and subtraction from left to right:

  • \(\frac{13}{2} + 2 = \frac{13}{2} + \frac{4}{2} = \frac{17}{2}\)
  • \(\frac{17}{2} - 1 = \frac{17}{2} - \frac{2}{2} = \frac{15}{2}\)

So, the simplified numerator is \(\frac{15}{2}\).

Simplifying the Denominator

Now, let's evaluate the denominator: \(11 \times 12 \div 12 + 12\)

Perform multiplication and division from left to right:

  • Multiplication: \(11 \times 12 = 132\)
  • The expression becomes: \(132 \div 12 + 12\)
  • Division: \(132 \div 12 = 11\)
  • The expression becomes: \(11 + 12\)

Finally, perform addition:

  • \(11 + 12 = 23\)

So, the simplified denominator is \(23\).

Combining Numerator and Denominator

The simplified fraction is the numerator divided by the denominator:

\(\frac{\text{Numerator}}{\text{Denominator}} = \frac{\frac{15}{2}}{23}\)

Dividing by a number is the same as multiplying by its reciprocal. The reciprocal of \(23\) is \(\frac{1}{23}\).

\(\frac{15}{2} \div 23 = \frac{15}{2} \times \frac{1}{23}\)

Multiply the numerators and the denominators:

\(\frac{15 \times 1}{2 \times 23} = \frac{15}{46}\)

The simplified expression is \(\frac{15}{46}\).

Part Original Expression Simplified Value
Numerator \(6\frac{1}{2} + 2\frac{5}{7} \times \frac{{14}}{{19}} - \frac{1}{2} \div 2\ of\frac{1}{4}\) \(\frac{15}{2}\)
Denominator \(11 \times 12 \div 12 + 12\) \(23\)
Overall Fraction \(\frac{\text{Numerator}}{\text{Denominator}}\) \(\frac{\frac{15}{2}}{23} = \frac{15}{46}\)

Comparing this result with the given options, we find that the simplified value matches Option 1.

Revision Table: Key Steps in Simplifying Expressions

Step Description Relevant Operations (BODMAS/PEDMAS)
1 Convert mixed numbers to improper fractions. Preparation
2 Evaluate operations within Brackets/Parentheses. B/P
3 Evaluate Orders (powers, roots) and 'Of'. O/O
4 Perform Division and Multiplication from left to right. D/M
5 Perform Addition and Subtraction from left to right. A/S
6 Combine numerator and denominator (if a fraction). Final Step

Additional Information: Working with Fractions and Operations

When working with fractions, remember these key points:

  • Mixed Numbers: Always convert mixed numbers to improper fractions before performing multiplication or division. They can be used directly in addition/subtraction sometimes, but improper fractions are generally safer for complex expressions.
  • 'Of' vs. Multiplication: 'Of' signifies multiplication, but it is typically evaluated before standard multiplication and division in the BODMAS/PEDMAS order.
  • Division by Fraction: Dividing by a fraction is equivalent to multiplying by its reciprocal. For example, \(a \div \frac{b}{c} = a \times \frac{c}{b}\).
  • Division by Whole Number: Dividing a fraction by a whole number (like \(\frac{a}{b} \div c\)) is equivalent to \(\frac{a}{b} \times \frac{1}{c}\).

Paying close attention to the order of operations and performing each step carefully is crucial for simplifying mathematical expressions correctly.

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Important Questions from Simplification

  1. The value of {5 - 5 ÷ (10 - 12) × 8 + 9} × 3 + 5 + 5 × 5 ÷ 5 of 5 is:

  2. What should come in place of the question mark (?) in the following question?

    [((16 ÷ 4) × 4) ÷ 4] = ?

  3. The value of \(\left( {\frac{7}{5} \div \frac{7}{{10}}of\frac{3}{4}} \right) \div \frac{4}{9} + \left( {\frac{7}{{16}} \div 10\frac{1}{2} \times 7\frac{1}{5}} \right) \times \frac{5}{{12}} \)  is:

  4. The value of \(\left( {{1 \over 2}} \right)\) [{–2(12 + 2)}10] is:

  5. \({{1} \over 3\times4} + {{1} \over 4\times5} + {{1} \over 5\times6} + ... + ...............{{1} \over 20\times21}\) On simplification, the given expression will give the result as:
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