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Fractions - Comparing Like and Unlike Fractions

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Understanding Fractions: A fraction is a part of a whole, written in the form ab\frac{a}{b}, where aa is the numerator (parts taken) and bb is the denominator (total parts). Visually, if you divide a rectangular chocolate bar into 44 equal pieces and eat 11, the fraction eaten is 14\frac{1}{4}.

Like Fractions: These are fractions that have the same denominator, such as 27\frac{2}{7} and 57\frac{5}{7}. When denominators are the same, the fraction with the larger numerator is the greater fraction. Visually, if two identical circles are both divided into 77 equal slices, 55 slices will cover a larger area than 22 slices.

Unlike Fractions with Same Numerator: If two fractions have the same numerator but different denominators (e.g., 13\frac{1}{3} and 15\frac{1}{5}), the fraction with the smaller denominator is larger. Visually, if you cut a pizza into 33 large slices, one slice is bigger than if you cut the same pizza into 55 smaller slices.

Unlike Fractions with Different Denominators: To compare fractions where both parts are different (e.g., 23\frac{2}{3} and 34\frac{3}{4}), we must first make them 'like' fractions by finding a common denominator, usually the Least Common Multiple (LCM) of the denominators.

Equivalent Fractions: These are fractions that represent the same value, even if they look different. For example, 12\frac{1}{2}, 24\frac{2}{4}, and 48\frac{4}{8} are all equivalent. Visually, shading half of a circle looks the same regardless of whether it is divided into 22 large parts or 88 small parts.

The Cross-Multiplication Rule: A quick way to compare any two fractions ab\frac{a}{b} and cd\frac{c}{d} is to cross-multiply. We compare the products a×da \times d and b×cb \times c. If a×da \times d is greater, then ab\frac{a}{b} is the larger fraction.

Ordering Fractions: Fractions can be arranged in Ascending Order (smallest to largest) or Descending Order (largest to smallest) by converting all given unlike fractions into like fractions using their LCM and then comparing their numerators.

📐Formulae

Like Fractions Comparison: If b=db = d, then ab>cd\frac{a}{b} > \frac{c}{d} if a>ca > c

Same Numerator Comparison: If a=ca = c, then ab>ad\frac{a}{b} > \frac{a}{d} if b<db < d

Cross-Multiplication Method: For ab\frac{a}{b} and cd\frac{c}{d}, calculate M=a×dM = a \times d and N=b×cN = b \times c. If M>NM > N, then ab>cd\frac{a}{b} > \frac{c}{d}

Equivalent Fraction: ab=a×nb×n\frac{a}{b} = \frac{a \times n}{b \times n} (where n0n \neq 0)

💡Examples

Problem 1:

Compare the fractions 35\frac{3}{5} and 47\frac{4}{7} to find which one is greater.

Solution:

Step 1: Find the LCM of the denominators 55 and 77. Since they are co-prime, LCM(5,7)=5×7=35LCM(5, 7) = 5 \times 7 = 35. \ Step 2: Convert both fractions to equivalent fractions with denominator 3535. \ 35=3×75×7=2135\frac{3}{5} = \frac{3 \times 7}{5 \times 7} = \frac{21}{35} \ 47=4×57×5=2035\frac{4}{7} = \frac{4 \times 5}{7 \times 5} = \frac{20}{35} \ Step 3: Compare the numerators of the like fractions. \ Since 21>2021 > 20, it follows that 2135>2035\frac{21}{35} > \frac{20}{35}. \ Therefore, 35>47\frac{3}{5} > \frac{4}{7}.

Explanation:

This solution uses the common denominator method. By making the parts the same size (35ths), we can directly compare how many parts each fraction has.

Problem 2:

Arrange the following fractions in ascending order: 23,16,59\frac{2}{3}, \frac{1}{6}, \frac{5}{9}.

Solution:

Step 1: Find the LCM of 3,6,3, 6, and 99. \ Multiples of 3:3,6,9,12,15,18...3: 3, 6, 9, 12, 15, 18... \ Multiples of 6:6,12,18...6: 6, 12, 18... \ Multiples of 9:9,18...9: 9, 18... \ So, LCM(3,6,9)=18LCM(3, 6, 9) = 18. \ Step 2: Convert to like fractions with denominator 1818. \ 23=2×63×6=1218\frac{2}{3} = \frac{2 \times 6}{3 \times 6} = \frac{12}{18} \ 16=1×36×3=318\frac{1}{6} = \frac{1 \times 3}{6 \times 3} = \frac{3}{18} \ 59=5×29×2=1018\frac{5}{9} = \frac{5 \times 2}{9 \times 2} = \frac{10}{18} \ Step 3: Compare numerators: 3<10<123 < 10 < 12. \ Thus, 318<1018<1218\frac{3}{18} < \frac{10}{18} < \frac{12}{18}. \ Final Answer: 16<59<23\frac{1}{6} < \frac{5}{9} < \frac{2}{3}.

Explanation:

To order multiple unlike fractions, we convert them all to a common denominator and then arrange them based on their numerators from smallest to largest.