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Simplification

Learning objective
Simplify numerical expressions using HCF and LCM

Introduction to Simplification in Arithmetic Operations

Simplification is the process of making a numerical expression easier to understand or calculate by reducing it to its simplest form. In arithmetic, this often means performing operations in the correct order and reducing fractions to their simplest terms. Simplification helps us solve problems quickly and accurately, especially in exams like the Assam Direct Recruitment Examination (ADRE) for Grade IV posts.

Two important tools in simplification are the Highest Common Factor (HCF) and the Least Common Multiple (LCM). These help us work efficiently with fractions and numerical expressions. Before we dive into these, it is essential to understand the order of operations, which tells us the correct sequence to solve expressions involving multiple operations.

Order of Operations

When an expression has more than one arithmetic operation, such as addition, subtraction, multiplication, division, or brackets, it is important to solve it in the right order. This avoids confusion and ensures everyone gets the same answer.

The rule to remember is called BODMAS or BIDMAS, which stands for:

  • Brackets - Solve expressions inside brackets first.
  • Orders (or Indices) - Solve powers and roots next.
  • Division and Multiplication - Solve from left to right.
  • Addition and Subtraction - Solve last, from left to right.

This order ensures clarity and correctness.

graph TD    A[Start] --> B[Brackets]    B --> C[Orders (powers/roots)]    C --> D[Division and Multiplication (left to right)]    D --> E[Addition and Subtraction (left to right)]    E --> F[End]

Example: Simplify \( 5 + 2 \times (8 - 3)^2 \div 5 \)

  • First, solve inside the brackets: \(8 - 3 = 5\)
  • Next, orders: \(5^2 = 25\)
  • Then, multiplication and division from left to right: \(2 \times 25 = 50\), then \(50 \div 5 = 10\)
  • Finally, addition: \(5 + 10 = 15\)

Answer: 15

Using HCF and LCM for Simplification

Before working with fractions or complex expressions, it is helpful to understand two key concepts:

Highest Common Factor (HCF)

The Highest Common Factor of two or more numbers is the largest number that divides all of them exactly without leaving a remainder.

Why is HCF important? When simplifying fractions, dividing both numerator and denominator by their HCF reduces the fraction to its simplest form.

Least Common Multiple (LCM)

The Least Common Multiple of two or more numbers is the smallest number that is a multiple of all of them.

Why is LCM important? When adding or subtracting fractions with different denominators, finding the LCM of the denominators helps us find a common denominator quickly.

Numbers HCF LCM
12 and 18 6 36
8 and 20 4 40
15 and 25 5 75

Simplifying Fractions Using HCF

To simplify a fraction:

  1. Find the HCF of the numerator and denominator.
  2. Divide both numerator and denominator by the HCF.
  3. The resulting fraction is in its simplest form.

Example: Simplify \(\frac{18}{24}\)

  • HCF of 18 and 24 is 6.
  • Divide numerator and denominator by 6: \(\frac{18 \div 6}{24 \div 6} = \frac{3}{4}\)
  • So, \(\frac{18}{24} = \frac{3}{4}\) in simplest form.

Adding Fractions Using LCM

When adding fractions with different denominators, follow these steps:

  1. Find the LCM of the denominators to get a common denominator.
  2. Convert each fraction to an equivalent fraction with the LCM as denominator.
  3. Add the numerators and keep the denominator same.
  4. Simplify the resulting fraction using HCF if possible.

Example: Add \(\frac{1}{3} + \frac{1}{4}\)

  • LCM of 3 and 4 is 12.
  • Convert fractions: \(\frac{1}{3} = \frac{4}{12}\), \(\frac{1}{4} = \frac{3}{12}\)
  • Add numerators: \(4 + 3 = 7\)
  • Result: \(\frac{7}{12}\) (already simplified)

Simplifying Numerical Expressions with Fractions and Brackets

Expressions often combine whole numbers, fractions, and brackets. Use the order of operations along with HCF and LCM to simplify efficiently.

For example, when you see an expression like \(2 \times \left(\frac{3}{4} + \frac{5}{6}\right) - 1\), first simplify inside the brackets by adding fractions using LCM, then multiply and subtract.

Summary

By following the BODMAS rule and using HCF and LCM to simplify fractions, you can solve complex arithmetic expressions step-by-step with confidence and accuracy. This approach reduces errors and saves time during exams.

Highest Common Factor (HCF)

\[HCF(a,b) = \text{Greatest number that divides both } a \text{ and } b \text{ exactly}\]

Used to simplify fractions by dividing numerator and denominator by their HCF

a, b = integers

Least Common Multiple (LCM)

\[LCM(a,b) = \frac{a \times b}{HCF(a,b)}\]

Used to find common denominators when adding or subtracting fractions

a, b = integers

Order of Operations (BODMAS)

\[Evaluate \text{expressions in the order: Brackets} > \text{Orders} > \text{Division/Multiplication} > \text{Addition/Subtraction}\]

Ensures correct evaluation of numerical expressions

Example 1: Simplify (12 / 3) + (8 / 4) Easy
Simplify the expression: \( (12 \div 3) + (8 \div 4) \)

Step 1: Solve inside the brackets separately.

\(12 \div 3 = 4\)

\(8 \div 4 = 2\)

Step 2: Add the results.

\(4 + 2 = 6\)

Answer: 6

Example 2: Simplify \(\frac{18}{24} + \frac{6}{8}\) Medium
Add and simplify the fractions: \(\frac{18}{24} + \frac{6}{8}\)

Step 1: Simplify each fraction.

HCF of 18 and 24 is 6, so \(\frac{18}{24} = \frac{3}{4}\).

HCF of 6 and 8 is 2, so \(\frac{6}{8} = \frac{3}{4}\).

Step 2: Add the simplified fractions.

\(\frac{3}{4} + \frac{3}{4} = \frac{6}{4}\)

Step 3: Simplify \(\frac{6}{4}\).

HCF of 6 and 4 is 2, so \(\frac{6}{4} = \frac{3}{2}\) or \(1 \frac{1}{2}\).

Answer: \(1 \frac{1}{2}\) or \(\frac{3}{2}\)

Example 3: Simplify \(2 \times \left(\frac{3}{4} + \frac{5}{6}\right) - 1\) Medium
Simplify the expression: \(2 \times \left(\frac{3}{4} + \frac{5}{6}\right) - 1\)

Step 1: Find LCM of denominators 4 and 6.

LCM(4,6) = 12.

Step 2: Convert fractions to have denominator 12.

\(\frac{3}{4} = \frac{9}{12}\), \(\frac{5}{6} = \frac{10}{12}\)

Step 3: Add the fractions inside the bracket.

\(\frac{9}{12} + \frac{10}{12} = \frac{19}{12}\)

Step 4: Multiply by 2.

\(2 \times \frac{19}{12} = \frac{38}{12}\)

Step 5: Simplify \(\frac{38}{12}\).

HCF of 38 and 12 is 2, so \(\frac{38}{12} = \frac{19}{6}\)

Step 6: Subtract 1.

Convert 1 to \(\frac{6}{6}\): \(\frac{19}{6} - \frac{6}{6} = \frac{13}{6}\)

Answer: \(\frac{13}{6}\) or \(2 \frac{1}{6}\)

Example 4: Simplify \(\frac{45}{60} - \frac{15}{20} + (6 \div 3)\) Hard
Simplify the expression: \(\frac{45}{60} - \frac{15}{20} + (6 \div 3)\)

Step 1: Simplify each fraction.

HCF of 45 and 60 is 15, so \(\frac{45}{60} = \frac{3}{4}\).

HCF of 15 and 20 is 5, so \(\frac{15}{20} = \frac{3}{4}\).

Step 2: Subtract the fractions.

\(\frac{3}{4} - \frac{3}{4} = 0\)

Step 3: Calculate \(6 \div 3 = 2\).

Step 4: Add the results.

\(0 + 2 = 2\)

Answer: 2

Example 5: Simplify \(\left(\frac{2}{3} + \frac{3}{4}\right) \times \frac{12}{15}\) Hard
Simplify the expression: \(\left(\frac{2}{3} + \frac{3}{4}\right) \times \frac{12}{15}\)

Step 1: Find LCM of denominators 3 and 4.

LCM(3,4) = 12.

Step 2: Convert fractions to denominator 12.

\(\frac{2}{3} = \frac{8}{12}\), \(\frac{3}{4} = \frac{9}{12}\)

Step 3: Add the fractions inside the bracket.

\(\frac{8}{12} + \frac{9}{12} = \frac{17}{12}\)

Step 4: Multiply by \(\frac{12}{15}\).

\(\frac{17}{12} \times \frac{12}{15} = \frac{17 \times 12}{12 \times 15} = \frac{17}{15}\)

Step 5: Simplify if possible.

17 and 15 have no common factors other than 1, so fraction is already simplified.

Answer: \(\frac{17}{15}\) or \(1 \frac{2}{15}\)

Formula Bank

Highest Common Factor (HCF)
\[ \text{HCF}(a,b) = \text{Greatest number that divides both } a \text{ and } b \text{ exactly} \]
where: \(a, b\) are integers
Least Common Multiple (LCM)
\[ \text{LCM}(a,b) = \frac{a \times b}{\text{HCF}(a,b)} \]
where: \(a, b\) are integers
Order of Operations (BODMAS)
\[ \text{Evaluate in order: Brackets} > \text{Orders} > \text{Division/Multiplication} > \text{Addition/Subtraction} \]
N/A

Tips & Tricks

Tip: Always simplify fractions by dividing numerator and denominator by their HCF before performing operations.

When to use: When adding, subtracting, or comparing fractions to reduce calculation complexity.

Tip: Find the LCM of denominators first when adding or subtracting fractions to get a common denominator quickly.

When to use: When dealing with addition or subtraction of fractions with different denominators.

Tip: Use the BODMAS rule strictly to avoid mistakes in multi-operation expressions.

When to use: While simplifying expressions with brackets, powers, multiplication, division, addition, and subtraction.

Tip: Break down complex expressions into smaller parts and simplify step-by-step.

When to use: When expressions have multiple brackets and mixed operations.

Tip: Double-check calculations involving fractions by converting to decimals if unsure.

When to use: To verify answers quickly during practice or exams.

Common Mistakes to Avoid

❌ Ignoring the order of operations and solving from left to right
✓ Always follow BODMAS/BIDMAS to solve brackets and operations in correct sequence
Why: Students often rush and overlook operation precedence, leading to wrong answers
❌ Not simplifying fractions before performing addition or subtraction
✓ Find HCF to simplify fractions first, then perform operations
Why: Skipping simplification makes calculations cumbersome and error-prone
❌ Using incorrect LCM leading to wrong common denominators
✓ Calculate LCM accurately using prime factorization or formula
Why: Incorrect LCM causes errors in fraction addition/subtraction
❌ Misplacing brackets or ignoring them during simplification
✓ Pay close attention to brackets and simplify expressions inside them first
Why: Brackets change the order of operations and ignoring them leads to wrong results
❌ Mixing up numerator and denominator when simplifying fractions
✓ Carefully divide both numerator and denominator by the HCF
Why: Confusion leads to incorrect fraction forms and wrong answers
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