Complete Guide to Fractions
1. Introduction to Fractions
A fraction represents a part of a whole. It consists of a numerator (top number) and a denominator (bottom number).
Basic Definition:
The numerator represents how many parts we have.
The denominator represents the total number of equal parts that make up a whole.
For example, in the fraction
3/4
1/2
Fractions are used to represent parts of a whole, to compare quantities, and to perform calculations in many real-world scenarios like cooking, measurement, time, and probability.
2. Types of Fractions
Proper Fractions:
A proper fraction has a numerator that is less than its denominator. The value of a proper fraction is always less than 1.
Examples of proper fractions:
One-half
Three-fourths
Five-eighths
Improper Fractions:
An improper fraction has a numerator that is greater than or equal to its denominator. The value of an improper fraction is always greater than or equal to 1.
Examples of improper fractions:
Five-thirds
Seven-fourths
Eleven-eighths
Mixed Numbers:
A mixed number consists of a whole number and a proper fraction. It represents a value that is greater than 1.
Examples of mixed numbers:
One and a half
Two and three-fourths
Three and five-eighths
Unit Fractions:
A unit fraction has a numerator of 1.
Examples of unit fractions:
One-half
One-fourth
One-tenth
Like and Unlike Fractions:
Like fractions have the same denominator.
Unlike fractions have different denominators.
Examples of like fractions:
Examples of unlike fractions:
Equivalent Fractions:
Equivalent fractions represent the same value even though they have different numerators and denominators.
Examples of equivalent fractions:
3. Equivalent Fractions
Creating Equivalent Fractions:
To create an equivalent fraction, multiply or divide both the numerator and denominator by the same non-zero number.
To find equivalent fractions for
- Multiply by 2: =2 × 23 × 246
- Multiply by 3: =2 × 33 × 369
- Multiply by 4: =2 × 43 × 4812
Simplifying Fractions:
To simplify a fraction to its lowest terms, divide both the numerator and denominator by their greatest common divisor (GCD).
To simplify
- Find the GCD of 12 and 18: GCD(12, 18) = 6
- Divide both numbers by the GCD: =12 ÷ 618 ÷ 623
Therefore,
Finding the Greatest Common Divisor (GCD):
There are several methods to find the GCD:
Method 1: Listing Factors
To find the GCD of 24 and 36:
- List the factors of 24: 1, 2, 3, 4, 6, 8, 12, 24
- List the factors of 36: 1, 2, 3, 4, 6, 9, 12, 18, 36
- Identify the common factors: 1, 2, 3, 4, 6, 12
- The greatest common factor is 12
Method 2: Prime Factorization
To find the GCD of 24 and 36:
- Prime factorization of 24: 23 × 3
- Prime factorization of 36: 22 × 32
- Take the common prime factors with the lowest exponents: 22 × 3
- Calculate: 22 × 3 = 4 × 3 = 12
Method 3: Euclidean Algorithm
To find the GCD of 24 and 36:
- Divide the larger number by the smaller: 36 ÷ 24 = 1 remainder 12
- Replace the larger number with the smaller, and the smaller with the remainder: GCD(24, 12)
- Repeat: 24 ÷ 12 = 2 remainder 0
- When the remainder is 0, the divisor is the GCD: GCD(24, 36) = 12
4. Comparing Fractions
Method 1: Using Common Denominators
To compare fractions with different denominators, convert them to equivalent fractions with a common denominator.
Compare
- Find the least common multiple (LCM) of the denominators: LCM(3, 5) = 15
- Convert the fractions to equivalent fractions with denominator 15:
- =23=2 × 53 × 51015
- =35=3 × 35 × 3915
- Compare the numerators: 10 > 9
- Therefore, >2335
Method 2: Cross Multiplication
Another method to compare fractions is to cross multiply.
Compare
- Cross multiply:
- 2 × 5 = 10
- 3 × 3 = 9
- Compare the products: 10 > 9
- Therefore, >2335
Method 3: Converting to Decimals
Convert the fractions to decimals and then compare the decimal values.
Compare
- = 2 ÷ 3 ≈ 0.66723
- = 3 ÷ 5 = 0.635
- Compare: 0.667 > 0.6
- Therefore, >2335
Method 4: Using a Number Line
Locate the fractions on a number line to compare their values.
Compare
On the number line, we can see that
Therefore,
Method 5: Using Benchmark Fractions
Compare fractions to common benchmark fractions like 0, 1/2, and 1.
Compare
- Compare each fraction to 1/2:
- <38=48(since 3 < 4)12
- >59=4.59(since 5 > 4.5)12
- Since <38and12>59, we can conclude that12<3859
5. Converting Fractions
Converting Improper Fractions to Mixed Numbers
To convert an improper fraction to a mixed number:
- Divide the numerator by the denominator
- The quotient becomes the whole number part
- The remainder becomes the numerator of the fractional part
- The denominator remains the same
Convert
- Divide: 17 ÷ 4 = 4 remainder 1
- Whole number part: 4
- Fractional part: 14
- Mixed number: 414
Converting Mixed Numbers to Improper Fractions
To convert a mixed number to an improper fraction:
- Multiply the whole number by the denominator
- Add the numerator to the product
- Use this sum as the new numerator over the original denominator
Convert
- Multiply the whole number by the denominator: 3 × 5 = 15
- Add the numerator: 15 + 2 = 17
- Use this sum as the new numerator: 175
Converting Fractions to Decimals
To convert a fraction to a decimal, divide the numerator by the denominator.
Convert
3 ÷ 4 = 0.75
Convert
2 ÷ 3 = 0.666... = 0.6̅ (the bar indicates that the digit repeats indefinitely)
Converting Decimals to Fractions
To convert a decimal to a fraction:
- For terminating decimals:
- Count the number of decimal places
- Multiply by the appropriate power of 10 to remove the decimal point
- Write as a fraction and simplify if possible
- For repeating decimals:
- Write as an equation involving variables
- Manipulate the equation to isolate the repeating part
- Solve for the variable to find the fraction
Convert 0.75 to a fraction:
- There are 2 decimal places, so multiply by 100: 0.75 × 100 = 75
- Write as a fraction: 75100
- Simplify: =7510034
Convert 0.333... to a fraction:
- Let x = 0.333...
- Multiply by 10: 10x = 3.333...
- Subtract the original equation: 10x - x = 3.333... - 0.333...
- Simplify: 9x = 3
- Solve for x: x = 3/9 = 1/3
Converting Fractions to Percentages
To convert a fraction to a percentage:
- Convert the fraction to a decimal
- Multiply by 100
- Add the % symbol
Convert
- Convert to a decimal: 3 ÷ 4 = 0.75
- Multiply by 100: 0.75 × 100 = 75
- Add the % symbol: 75%
Converting Percentages to Fractions
To convert a percentage to a fraction:
- Remove the % symbol and divide by 100
- Simplify the fraction if possible
Convert 25% to a fraction:
- Remove the % symbol and divide by 100: 25100
- Simplify: =2510014
6. Operations with Fractions
Adding Fractions
Adding Fractions with Like Denominators
To add fractions with the same denominator, add the numerators and keep the denominator the same.
Add
- +38=28=3 + 2858
Adding Fractions with Unlike Denominators
To add fractions with different denominators:
- Find the least common multiple (LCM) of the denominators
- Convert each fraction to an equivalent fraction with the LCM as the denominator
- Add the numerators and keep the common denominator
- Simplify the result if possible
Add
- Find the LCM of 3 and 4: LCM(3, 4) = 12
- Convert to equivalent fractions with denominator 12:
- =23=2 × 43 × 4812
- =14=1 × 34 × 3312
- Add the numerators: +812=3121112
Adding Mixed Numbers
To add mixed numbers, you can either:
- Add the whole numbers and fractions separately, then combine.
- Convert mixed numbers to improper fractions, add, then convert back.
Add
Method 1: Add parts separately
- Add whole numbers: 2 + 1 = 3
- Add fractions: +3512
- Find LCM of denominators: LCM(5, 2) = 10
- Convert to equivalent fractions: =35and610=12510
- Add: +610=510=11101110
- Combine: 3 + =11104110
Method 2: Convert to improper fractions
- Convert to improper fractions:
- =235=2 × 5 + 35135
- =112=1 × 2 + 1232
- Add the fractions:
- Find LCM of denominators: LCM(5, 2) = 10
- Convert to equivalent fractions: =135and2610=321510
- Add: +2610=15104110
- Convert back to a mixed number:
- =41104110
Subtracting Fractions
Subtracting Fractions with Like Denominators
To subtract fractions with the same denominator, subtract the numerators and keep the denominator the same.
Subtract
- -78=38=7 - 38=4812
Subtracting Fractions with Unlike Denominators
To subtract fractions with different denominators:
- Find the least common multiple (LCM) of the denominators
- Convert each fraction to an equivalent fraction with the LCM as the denominator
- Subtract the numerators and keep the common denominator
- Simplify the result if possible
Subtract
- Find the LCM of 6 and 3: LCM(6, 3) = 6
- Convert to equivalent fractions with denominator 6:
- is already in terms of 656
- =13=1 × 23 × 226
- Subtract the numerators: -56=26=3612
Subtracting Mixed Numbers
To subtract mixed numbers, you can either:
- Subtract the whole numbers and fractions separately, then combine.
- Convert mixed numbers to improper fractions, subtract, then convert back.
Subtract
Method 1: Subtract parts separately (with regrouping if needed)
- Compare the fractions: >34, so no regrouping is needed13
- Subtract whole numbers: 5 - 2 = 3
- Subtract fractions: -3413
- Find LCM of denominators: LCM(4, 3) = 12
- Convert to equivalent fractions: =34and912=13412
- Subtract: -912=412512
- Combine: 3 + =5123512
Method 2: Convert to improper fractions
- Convert to improper fractions:
- =534=5 × 4 + 34234
- =213=2 × 3 + 1373
- Subtract the fractions:
- Find LCM of denominators: LCM(4, 3) = 12
- Convert to equivalent fractions: =234and6912=732812
- Subtract: -6912=28124112
- Convert back to a mixed number:
- =41123512
Subtract
Method 1: Subtract parts separately (with regrouping)
- Compare the fractions: <14, so regrouping is needed23
- Rewrite as314(borrowed 1 from the whole number)254
- Subtract whole numbers: 2 - 1 = 1
- Subtract fractions: -5423
- Find LCM of denominators: LCM(4, 3) = 12
- Convert to equivalent fractions: =54and1512=23812
- Subtract: -1512=812712
- Combine: 1 + =7121712
Multiplying Fractions
Multiplying Fractions
To multiply fractions:
- Multiply the numerators together
- Multiply the denominators together
- Simplify the result if possible
Multiply
- Multiply numerators: 2 × 3 = 6
- Multiply denominators: 3 × 5 = 15
- Result: =61525
Multiplying Mixed Numbers
To multiply mixed numbers:
- Convert mixed numbers to improper fractions
- Multiply the fractions as usual
- Convert the result back to a mixed number if appropriate
Multiply
- Convert to improper fractions:
- =11232
- =21373
- Multiply the fractions:
- ×32=73216
- Convert to a mixed number:
- =216=336312
Cancellation Method
To simplify multiplication of fractions, you can cancel common factors before multiplying.
Multiply
- Identify common factors:
- Common factor between 3 and 15: 3
- Common factor between 4 and 8: 4
- Cancel these factors:
- ×34=815×14=85×11=2525
Dividing Fractions
Dividing Fractions
To divide fractions:
- Take the reciprocal (flip) of the second fraction
- Multiply the first fraction by the reciprocal of the second fraction
- Simplify the result if possible
Divide
- Take the reciprocal of :2332
- Multiply: ×34=32=98118
Dividing Mixed Numbers
To divide mixed numbers:
- Convert mixed numbers to improper fractions
- Take the reciprocal of the second fraction
- Multiply the fractions
- Convert the result back to a mixed number if appropriate
Divide
- Convert to improper fractions:
- =31272
- =11454
- Take the reciprocal of the second fraction:
- Reciprocal of is5445
- Reciprocal of
- Multiply:
- ×72=45=2810145
- Convert to a mixed number:
- =145245
Dividing a Whole Number by a Fraction
To divide a whole number by a fraction:
- Convert the whole number to a fraction with denominator 1
- Take the reciprocal of the second fraction
- Multiply the fractions
Divide 6 ÷
- Convert 6 to a fraction: 61
- Take the reciprocal of :2332
- Multiply: ×61=32= 9182
7. Fraction Word Problems
Part of a Whole:
A recipe calls for 3/4 cup of flour. If you want to make 1/2 of the recipe, how much flour do you need?
Solution: To find half of 3/4 cup, multiply 3/4 by 1/2.
Comparing Fractions:
Sarah ate 2/3 of her pizza, and Michael ate 3/4 of his pizza. Who ate more of their pizza?
Solution: Compare the fractions 2/3 and 3/4.
Convert to equivalent fractions with a common denominator:
Since 9/12 > 8/12, Michael ate more of his pizza.
Adding and Subtracting Fractions:
A carpenter has a board that is 8 1/2 feet long. He cuts off a piece that is 3 3/4 feet long. How long is the remaining piece?
Solution: Subtract 3 3/4 from 8 1/2.
Convert to improper fractions:
Find a common denominator:
The remaining piece is 4 3/4 feet long.
Multiplying Fractions:
A recipe calls for 2/3 cup of sugar. If you want to make 1 1/2 batches of the recipe, how much sugar do you need?
Solution: Multiply 2/3 by 1 1/2.
Convert the mixed number to an improper fraction:
Multiply:
You need 1 cup of sugar.
Dividing Fractions:
A pitcher contains 3 1/4 gallons of water. If each glass holds 1/2 gallon, how many glasses can be filled?
Solution: Divide 3 1/4 by 1/2.
Convert the mixed number to an improper fraction:
Multiply by the reciprocal:
6 full glasses can be filled, with half a glass remaining.
8. Real-World Applications
Cooking and Recipes:
Fractions are commonly used in recipes to specify ingredient quantities and to scale recipes up or down.
A recipe calls for 3/4 cup of milk, 1/2 cup of sugar, and 1 1/4 cups of flour. How much of each ingredient is needed to make 3 batches?
Milk:
Sugar:
Flour:
Measurement:
Fractions are used in measurements for length, weight, volume, and time.
A board is 8 1/2 feet long. If it is cut into 4 equal pieces, how long is each piece?
A carpenter needs to make a cut at 3/8 of an inch from the edge of a board. If the ruler shows markings for 1/16 of an inch, how many markings should the carpenter count?
The carpenter should count 6 markings from the edge.
Finance:
Fractions are used in finance for interest rates, discounts, and investments.
A store offers a 1/3 discount on all items. If a shirt originally costs $36, what is the discounted price?
Original price = $36
Discount amount =
Discounted price = $36 - $12 = $24
If 3/4 of your monthly salary goes to expenses, and your salary is $2,800, how much money do you have left for savings?
Amount for expenses =
Amount for savings = $2,800 - $2,100 = $700
Probability and Statistics:
Fractions are used to express probabilities and statistical data.
A bag contains 5 red marbles, 3 blue marbles, and 2 green marbles. What is the probability of drawing a blue marble?
Total number of marbles = 5 + 3 + 2 = 10
Probability of drawing a blue marble =
In a survey, 3/5 of respondents preferred product A, while the rest preferred product B. If there were 200 respondents, how many preferred each product?
Number preferring product A =
Number preferring product B = 200 - 120 = 80
Construction and Engineering:
Fractions are essential in construction, carpentry, and engineering for precise measurements and calculations.
A blueprint uses a scale where 1/4 inch represents 1 foot. If a wall is 20 feet long, how long will it be on the blueprint?
A bolt with a diameter of 5/8 inch needs to fit through a hole. If the hole diameter is 3/4 inch, what is the clearance (difference between hole and bolt diameter)?
Music:
Fractions are used to represent different note durations in music.
In music notation, notes are represented as fractions of a whole note:
- A whole note = 1
- A half note = of a whole note12
- A quarter note = of a whole note14
- An eighth note = of a whole note18
- A sixteenth note = of a whole note116
If a song has 12 measures, and each measure contains 4 quarter notes, how many eighth notes would the entire song contain?
Number of quarter notes = 12 × 4 = 48
Number of eighth notes = 48 × 2 = 96 (since each quarter note equals 2 eighth notes)
9. Common Mistakes with Fractions
Adding or Subtracting Denominators:
A common mistake is to add or subtract the denominators when adding or subtracting fractions.
INCORRECT:
CORRECT:
Multiplying Numerators and Denominators in Addition:
Another common mistake is to multiply the numerators and denominators when adding fractions.
INCORRECT:
CORRECT:
Adding Whole Numbers and Fractions Separately:
When adding mixed numbers, a common mistake is to add the whole numbers and fractions separately without handling the case where the sum of fractions is greater than 1.
INCORRECT:
CORRECT:
Forgetting to Find the Least Common Multiple:
When adding or subtracting fractions, you need to find the least common multiple (LCM) of the denominators, not just any common multiple.
INEFFICIENT:
This is correct but using the LCM is more efficient when dealing with fractions with larger denominators.
Incorrect Simplification:
Simplifying fractions incorrectly by not dividing both the numerator and denominator by the same common factor.
INCORRECT:
CORRECT:
10. Interactive Fractions Quiz
Test Your Fractions Skills
Try these problems and check your answers:


