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Comparing Unlike Fractions Explained Clearly

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How to Compare Unlike Fractions Using LCM and Cross Multiplication

There are several ways we use fractions unknowingly while performing our day to day activities. It is fair to say that the world would not be without fractions as we see it today. One can compare fractions with unlike denominators by finding the least common denominator, or the smallest multiple the denominators share. Then we tend to make equivalent fractions, or fractions that represent the constant part of the total. As an example $\dfrac{1}{2}, \dfrac{1}{3}, \dfrac{1}{4}, \dfrac{1}{5}$ these are unlike fractions.


What is Fraction?

The terms used to determine the parts of a whole object are called fractions. For example, a pizza is divided into 4 pieces, so each piece of it is represented as $\dfrac{1}{4}$th of the pizza. Here 1 will be the numerator and 4 will be the denominator.


Types of Fraction

On the basis of numerator and denominator, apart from these three main types of fractions, there are three more types of fractions namely like & unlike fractions and equivalent fractions. Hence, there are total 6 types of fractions such as:

  1. Proper Fraction

  2. Improper Fraction

  3. Mixed Fraction

  4. Like Fractions

  5. Unlike Fractions

  6. Equivalent Fractions


Note: The primary three fractions are defined for a single fraction however the other three fractions determine the comparison between two or more fractions.


Unlike Fractions

Unlike fractions, fractions which have unequal denominators or different denominators. As an example $\dfrac{1}{2}, \dfrac{1}{3}, \dfrac{1}{4}, \dfrac{1}{5}$, were unlike fractions.

Simplification for such fractions is a little lengthy method since we need to factorize the denominator first and then simplify them (in case of addition and subtraction).

  • Suppose, we have to add $\dfrac{1}{2}$ and $\dfrac{1}{3}$. First of all we will find the LCM of 2 and 3 which is equal to 6.

  • Then we will multiply $\dfrac{1}{2}$ by 3 and $\dfrac{1}{3}$ by 2, in both the numerator and denominator.

  • The fractions will become $\dfrac{3}{6}$ and $\dfrac{2}{6}$.

  • Then, if $\dfrac{3}{6}$ and $\dfrac{2}{6}$ are added , we get;

  • $\dfrac{3}{6}+\dfrac{2}{6}=\dfrac{5}{6}$

Comparing Fractions

To compare unlike fractions, we change the unlike fractions to like fractions and then compare.


On comparison of two fractions with equal numerator,

$\dfrac{4}{7} \text { and } \dfrac{4}{9}$ whose numerator is the same.


Comparison of unlike fractions


Comparison of unlike fractions


Since 4 shaded elements of 7 is larger than the 4 shaded elements of 9 thus, $\dfrac{4}{7}>\dfrac{4}{9}$


To compare two fractions with totally different numerators and denominators, we multiply by a number to convert them into like fractions.


Solved Examples

Q 1. Which one is greater, $\dfrac{4}{7}$ Or $\dfrac{3}{5}$

Ans: First we convert these fractions into like fractions. To convert unlike fractions into like fractions first of all find the L.C.M. of their denominators.

L.C.M. of 7 and 5 will be $=35$

Now, On dividing the L.C.M. by the denominator of both fractions.

$35 \div 7=5$

$35 \div 5=7$

On Multiplying both the numerator and denominator with the number we get after dividing.

i.e.,

$\dfrac{4 \times 5}{7 \times 5}=\dfrac{20}{35}$

$\dfrac{3 \times 7}{5 \times 7}=\dfrac{21}{35}$

because, $\dfrac{21}{35}>\dfrac{20}{35}$ (because the denominator is the same and hence by checking the numerator, $21>20)$

So,

$\dfrac{3}{5}>\dfrac{4}{7}$

One can compare the two fractions by cross multiplication method also.

On solving the above example by cross multiplication. We will cross-multiply as follows.

$4 \times 5=20$

$3 \times 7=21$

Since, $21>20$

Therefore, $\dfrac{3}{5}>\dfrac{4}{7}$


Practice Questions

Write the correct comparison symbol.

Q 1. $\dfrac{2}{10} \square \dfrac{2}{5}$

Ans: $\dfrac{2}{10} < \dfrac{2}{5}$


Q 2. $\dfrac{1}{10} \square \dfrac{1}{5}$

Ans: $\dfrac{1}{10} < \dfrac{1}{5}$


Q 3. $\dfrac{3}{4} \square \dfrac{4}{7}$

Ans: $\dfrac{3}{4} > \dfrac{4}{7}$

Summary

In this Article about unlike fractions we have learnt that one can compare fractions with unlike denominators by finding the least common denominator, or the smallest multiple the denominators share. Then we tend to make equivalent fractions, or fractions that represent the constant part of the total And practice questions which will help to grasp the topic more easily. This blog shed light on fractions and how they are applied in different mathematics branches and how they impact our everyday life.

FAQs on Comparing Unlike Fractions Explained Clearly

1. What are unlike fractions?

Unlike fractions are fractions with different denominators. Unlike fractions do not have the same bottom number, so they cannot be directly added or compared without making their denominators the same.

  • Example: 1/3 and 1/5 are unlike fractions.
  • Example: 2/7 and 4/9 are unlike fractions.
  • They must be converted to like fractions before comparison or addition.

2. How do you compare unlike fractions?

To compare unlike fractions, first convert them into like fractions with a common denominator. This allows accurate comparison of numerators.

  • Step 1: Find the LCM of the denominators.
  • Step 2: Convert each fraction into an equivalent fraction.
  • Step 3: Compare the numerators.
Example: Compare 2/3 and 3/4.
LCM of 3 and 4 = 12.
2/3 = 8/12, 3/4 = 9/12.
Since 9/12 > 8/12, 3/4 is greater.

3. What is the formula for comparing unlike fractions?

Unlike fractions can be compared using the cross-multiplication method: if a/b and c/d are fractions, compare a × d and b × c.

  • If a × d > b × c, then a/b > c/d.
  • If a × d < b × c, then a/b < c/d.
Example: Compare 3/5 and 4/7.
3 × 7 = 21 and 5 × 4 = 20.
Since 21 > 20, 3/5 is greater.

4. How do you find the LCM when comparing unlike fractions?

To find the LCM for unlike fractions, list multiples of the denominators or use prime factorization to get the least common multiple (LCM).

  • Example: Denominators 6 and 8.
  • Multiples of 6: 6, 12, 18, 24...
  • Multiples of 8: 8, 16, 24...
  • LCM = 24.
The LCM becomes the common denominator for comparison.

5. Can you compare unlike fractions without finding the LCM?

Yes, unlike fractions can be compared using cross-multiplication without explicitly finding the LCM. This method is faster for two fractions.

  • Example: Compare 5/8 and 7/10.
  • 5 × 10 = 50
  • 8 × 7 = 56
  • Since 56 > 50, 7/10 is greater.
This avoids converting to equivalent fractions.

6. How do you arrange unlike fractions in ascending order?

To arrange unlike fractions in ascending order, convert them into like fractions using a common denominator, then compare numerators.

  • Example: 1/2, 2/3, 3/4
  • LCM of 2, 3, 4 = 12
  • 1/2 = 6/12, 2/3 = 8/12, 3/4 = 9/12
  • Ascending order: 1/2, 2/3, 3/4

7. What is the difference between like and unlike fractions?

Like fractions have the same denominators, while unlike fractions have different denominators.

  • Like fractions example: 3/8 and 5/8
  • Unlike fractions example: 3/8 and 5/6
  • Like fractions can be compared directly.
  • Unlike fractions require a common denominator or cross-multiplication.

8. How do you compare three or more unlike fractions?

To compare three or more unlike fractions, convert all fractions into equivalent fractions with a common denominator (LCM).

  • Example: 1/3, 1/4, 1/6
  • LCM of 3, 4, 6 = 12
  • 1/3 = 4/12, 1/4 = 3/12, 1/6 = 2/12
  • Greatest is 1/3, smallest is 1/6.

9. Why do we need a common denominator to compare unlike fractions?

A common denominator is needed because fractions represent parts of different-sized wholes, and comparison requires the same-sized parts.

  • 1/2 and 1/3 have different whole divisions.
  • Convert to 3/6 and 2/6.
  • Now comparison is clear since denominators are equal.
Using a common denominator ensures accurate comparison.

10. What are common mistakes when comparing unlike fractions?

A common mistake when comparing unlike fractions is comparing numerators or denominators directly without making them like fractions.

  • Wrong: Saying 3/8 > 5/6 because 8 > 6.
  • Correct method: Use LCM or cross-multiplication.
  • Always ensure denominators are equal before comparing numerators.
Avoiding these errors ensures correct comparison of unlike fractions.