# Division Lesson: Key Concepts, Strategies, and Solved Problems

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Janaisa Harris, an experienced educator, has devoted 4 years to teaching high school math and 6 years to tutoring. She holds a bachelor's degree in Mathematics (Secondary Education, and Teaching) from the University of North Carolina at Greensboro and is currently employed at Wilson County School (NC) as a mathematics teacher.
, BA (Mathematics)
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## Introduction to Division Lesson

Division is one of the four fundamental arithmetic operations, alongside addition, subtraction, and multiplication. It allows us to understand how a whole can be split into equal parts or how one quantity can be distributed among others. This division lesson will provide a thorough understanding of division, starting with its foundational principles and progressing to more advanced division techniques. We will explore division with whole numbers, fractions, decimals, and powers, ensuring a detailed grasp of each concept.

This lesson will cover various division strategies, division methods, and division exercises to help you master division problems effectively. By learning these division skills, you will be well-prepared to handle various mathematical challenges and apply them to real-life situations.

## What Is Division?

Division is a fundamental arithmetic operation that involves determining how many times one number (the divisor) is contained within another number (the dividend). The result of this operation is called the quotient. In simple terms, division is the process of splitting a quantity into equal parts or groups.

For example, in the equation 12 ÷ 3 = 4

• 12 is the dividend (the number being divided),
• 3 is the divisor (the number by which the dividend is divided), and
• 4 is the quotient (the result of the division).

There is also a remainder when the division is not exact. For example, in the equation 17 ÷ 5, the quotient is 3, and the remainder is 2. This type of division is known as long division, where the quotient represents the whole number part, and the remainder represents what is left over.

The division is often visualized as repeated subtraction. For example, dividing 15 by 3 can be thought of as repeatedly subtracting 3 from 15 until zero is reached. The number of times subtraction occurs is the quotient. In this sense, division and multiplication are inversely related; knowing this relationship can help in understanding and solving problems that involve both operations.

## What Are the Basic Principles of Division?

• The basic principles of division are essential for understanding how the operation works and how it can be applied in different mathematical contexts.

Here are the detailed explanations of these principles
• Dividend and Divisor
The dividend is the number that is being divided, while the divisor is the number by which the dividend is divided. It is crucial to correctly identify these roles to set up and solve division problems accurately. For example, in 20 ÷ 4 = 5, 20 is the dividend, and 4 is the divisor.
• Quotient and Remainder
The quotient is the result obtained after dividing the dividend by the divisor. When the division is not exact, there is a remainder. For example, in 23 ÷ 5, the quotient is 4, and the remainder is 3. This principle is important when dealing with whole numbers or when the result needs to be expressed as a mixed number or decimal.
• Inverse Relationship with Multiplication
Division can be considered the inverse (or opposite) of multiplication. This means that division reverses the process of multiplication. If 4 × 5 = 20, then 20 ÷ 5 = 4. This principle is especially useful in algebra and helps in checking the accuracy of division by reversing the operation through multiplication.
• Zero Division Rule
Division by zero is undefined. Dividing a number by zero does not have a meaningful result in mathematics. For example, 5 ÷ 0 is undefined because there is no number that you can multiply by 0 to get 5. This principle is fundamental to understanding the limitations of division in mathematical operations.

## What Are the Divisibility Rules?

Divisibility rules are shortcuts that help determine whether a given number can be divided by another number without leaving a remainder. These rules simplify division problems and make mental calculations faster.

Here are some important divisibility rules

• Divisibility by 2
A number is divisible by 2 if its last digit is even (0, 2, 4, 6, or 8). For example, 48 is divisible by 2 because its last digit is 8.
• Divisibility by 3
A number is divisible by 3 if the sum of its digits is divisible by 3. For example, 123 is divisible by 3 because 1 + 2 + 3 = 6, which is divisible by 3.
• Divisibility by 4
A number is divisible by 4 if the last two digits form a number that is divisible by 4. For example, 312 is divisible by 4 because the last two digits (12) are divisible by 4.
• Divisibility by 5
A number is divisible by 5 if its last digit is 0 or 5. For example, 85 is divisible by 5 because its last digit is 5.
• Divisibility by 6
A number is divisible by 6 if it is divisible by both 2 and 3. For example, 72 is divisible by 6 because it is divisible by 2 (last digit is 2) and by 3 (sum of digits is 9).
• Divisibility by 10
A number is divisible by 10 if its last digit is 0. For example, 100 is divisible by 10 because its last digit is 0.

These rules are particularly helpful when simplifying fractions, finding factors, or quickly performing division operations without a calculator.

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## How Do You Divide Fractions?

Dividing fractions involves a few straightforward steps, and understanding these steps is essential for solving problems involving fractions.

Here is a detailed explanation along with examples

1. Invert the Divisor (Reciprocal)
To divide by a fraction, you multiply by its reciprocal. For example, to divide 3/4 by 1/2, you would multiply 3/4 by 2/1.
2. Multiply the Fractions
Multiply the numerators together and the denominators together. For example, (3/4) × (2/1) = 6/4.
3. Simplify the Fraction
Reduce the fraction to its simplest form by dividing both the numerator and the denominator by their greatest common divisor (GCD). In the example above, 6/4 simplifies to 3/2.

#### Example 1: Dividing Fractions with the Same Denominator

To divide 5/8 by 3/8

• Invert the divisor 3/8 becomes 8/3.
• Multiply (5/8) × (8/3) = 40/24.
• Simplify 40/24 reduces to 5/3.

#### Example 2 : Dividing Fractions with Different Denominators

To divide 2/5 by 3/4

• Invert the divisor 3/4 becomes 4/3.
• Multiply (2/5) × (4/3) = 8/15.
• Simplify The fraction is already in its simplest form.

## How Do You Divide Decimals?

Dividing decimals involves a few key steps to ensure the correct result.

Here is a detailed explanation along with examples

1. Align the Decimal Points
Move the decimal point of the divisor to the right to make it a whole number. Move the decimal point of the dividend the same number of places.
2. Divide as with Whole Numbers
Perform the division as you would with whole numbers.
3. Place the Decimal Point in the Quotient
Ensure the decimal point in the quotient is aligned with the decimal points of the numbers being divided.

#### Example 1: Dividing Simple Decimals

To divide 6.4 by 2

• Align the decimal points.
• Divide normally 6.4 ÷ 2 = 3.2.
• The decimal point in the quotient is aligned with the numbers being divided.

#### Example 2: Dividing Decimals with Different Number of Decimal Places

To divide 10.5 by 0.35

• Move the decimal point in 0.35 two places to the right, making it 35. Do the same for 10.5, making it 1050.
• Divide normally: 1050 ÷ 35 = 30.
• The result is 30.

## How Do You Divide Powers?

Dividing powers involves specific rules when the powers share the same base.

Here is a detailed explanation along with examples

1. Ensure Same Base
To divide powers, the terms must have the same base.
2. Subtract the Exponents
When the bases are the same, subtract the exponents. For example, x5 ÷ x2 = x(5-2) = x3.
3. Maintain the Base
The base remains unchanged after subtracting the exponents.

#### Example 1: Dividing Powers with the Same Base

To divide 85 by 83

• Ensure the base is the same: both terms have the base 8.
• Subtract the exponents 5 - 3 = 2.
• The result is 82.

#### Example 2: Dividing Larger Powers with the Same Base

To divide 56 by 52:

• Ensure the base is the same: both terms have the base 5.
• Subtract the exponents: 6 - 2 = 4.
• The result is 54.

## How Do You Perform Mental Division?

Mental division techniques help simplify division problems and make calculations faster without the need for paper or a calculator.

Here are some mental division strategies

• Breaking Down the Dividend
Break down the dividend into smaller, more manageable parts. For example, to divide 96 by 4, think of 96 as (80 + 16), and divide each part separately: 80 ÷ 4 = 20 and 16 ÷ 4 = 4. The result is 20 + 4 = 24.
• Using Multiplication Facts
Use known multiplication facts to quickly determine the quotient. For example, if you know that 8 × 7 = 56, you can easily find that 56 ÷ 8 = 7.
• Compatible Numbers
Round numbers to make division easier. For example, dividing 198 by 6 can be approximated by dividing 200 by 6.

## What Are the Properties of Division?

Division has several important properties that distinguish it from other arithmetic operations like addition and multiplication. Understanding these properties helps in correctly solving division problems and recognizing how division behaves in different scenarios.

Here are the detailed explanations of these properties

• Non-Commutativity
Division is not commutative, which means that changing the order of the numbers changes the result. For example, 12 ÷ 4 is not the same as 4 ÷ 12. In division, the order of the numbers is crucial because reversing them will lead to a different outcome.
• Non-Associativity
Division is not associative, meaning that the grouping of numbers affects the result. For example, (20 ÷ 5) ÷ 2 is not the same as 20 ÷ (5 ÷ 2). This property indicates that when dividing three or more numbers, the way in which the numbers are grouped will affect the final result.
• Division by One
Any number divided by 1 remains unchanged. For example, 9 ÷ 1 = 9. This property emphasizes that dividing a number by one does not change its value.
• Division by Itself
Any number divided by itself equals 1, except for 0. For example, 7 ÷ 7 = 1. This property is useful in solving equations and understanding the concept of ratios.

## What Are the Various Types of Division?

Division can be categorized into various types based on how it is applied in mathematics. Each type of division has unique characteristics, rules, and applications. Here are the detailed explanations of the various types of division, along with comprehensive examples to illustrate each type:

1. Simple Division
Simple division, also known as basic division, involves dividing one number (the dividend) by another number (the divisor) to obtain a quotient. It deals with whole numbers and is the most fundamental form of division taught in elementary mathematics.
Example
Consider dividing 20 by 4. Here, 20 is the dividend (the number to be divided), and 4 is the divisor (the number by which the dividend is divided). The quotient, which is the result, is 5. The division is expressed as 20 divided by 4 equals 5. This simple division shows that 20 contains four 5s.
2. Long Division
Long division is a method used for dividing large numbers by breaking down the division process into smaller, more manageable steps. It involves dividing, multiplying, subtracting, and bringing down the next digit sequentially until the division is complete. Long division is useful when the dividend and divisor are large or when the divisor is not a simple number.
Example
Divide 987 by 32 using long division.
Step-by-step
• First, divide 98 by 32, which goes 3 times (since 32 times 3 equals 96). Write 3 above the 8 in 987.
• Subtract 96 from 98 to get 2.
• Bring down the next digit, 7, making it 27.
• Now divide 27 by 32, which goes 0 times. Write 0 above the 7.
• Since 32 is larger than 27, this completes the process. The quotient is 30, and the remainder is 27.
This shows that 987 divided by 32 results in a quotient of 30 with a remainder of 27.
3. Short Division
Short division is a simplified version of long division, typically used when the divisor is a small number. It requires less writing and is faster than long division but relies on mental arithmetic skills to carry out the steps.
Example
Divide 456 by 4 using short division.
• Divide the hundreds digit (4) by 4 to get 1.
• Divide the tens digit (5) by 4 to get 1 with a remainder of 1 (since 4 times 1 equals 4 and 5 minus 4 equals 1).
• Combine the remainder with the next digit to get 16. Divide 16 by 4 to get 4.
• The result is 114, meaning 456 divided by 4 equals 114.
4. Division of Fractions
Dividing fractions involves multiplying the first fraction (dividend) by the reciprocal of the second fraction (divisor). This method simplifies the division process and makes it easy to calculate the quotient.
Example
Divide 3/4 by 1/2.
• To divide fractions, first take the reciprocal of the divisor (second fraction), so 1/2 becomes 2/1.
• Now multiply: 3/4 times 2/1 equals 6/4.
• Simplify the fraction: 6/4 equals 3/2.
• Thus, 3/4 divided by 1/2 equals 3/2. This shows that dividing 3/4 by 1/2 is equivalent to finding how many 1/2s fit into 3/4, which is 3/2.
5. Decimal Division
Decimal division involves dividing numbers that contain decimals. The process is similar to simple division but requires aligning decimal points and adjusting them accordingly during the division process.
Example
Divide 15.6 by 1.2.
• First, shift the decimal point in both numbers to the right to make the divisor a whole number. Here, 1.2 becomes 12, and 15.6 becomes 156.
• Now divide 156 by 12:
• 12 goes into 15 once. Subtract 12 from 15 to get 3, and bring down the 6, making it 36.
• 12 goes into 36 exactly 3 times.
• The result is 13.
This shows that 15.6 divided by 1.2 equals 13.
6. Division with Remainders
Division with remainders is a type of division where the dividend is not completely divisible by the divisor. The result includes both a quotient and a remainder.
Example
Divide 17 by 5.
• 5 goes into 17 three times (since 5 times 3 equals 15).
• Subtract 15 from 17 to get a remainder of 2.
• Thus, 17 divided by 5 equals 3 with a remainder of 2.
This means that 17 is made up of three 5s with 2 left over.
7. Synthetic Division
Synthetic division is a shortcut method for dividing a polynomial by a linear divisor of the form x - c. It is a simplified version of the polynomial long division and is particularly useful in algebra for finding zeros of polynomials and simplifying expressions.
Example
Divide the polynomial 2x3 + 3x2 - 4x + 5 by x - 1 using synthetic division.
• Write down the coefficients: 2, 3, -4, 5.
• Write the zero of the divisor, x - 1 equals 0, therefore x equals 1.
• Bring down the first coefficient (2). Multiply it by 1 and write it under the next coefficient. Add to get 5.
• Repeat this process: Multiply 5 by 1, add to -4 to get 1. Multiply 1 by 1, add to 5 to get 6.
• The final row gives the coefficients of the quotient: 2x2 + 5x + 1, and the remainder is 6.
This means that dividing 2x3 + 3x2 - 4x + 5 by x - 1 results in 2x2 + 5x + 1 with a remainder of 6.
8. Euclidean Division
Euclidean division is a form of division applied in number theory. It refers to the process of dividing two integers to obtain a quotient and a remainder. This type is the basis for the Euclidean algorithm, which is used to find the greatest common divisor (GCD) of two numbers.
Example
Divide 101 by 7 using Euclidean division.
• 7 goes into 101 fourteen times (since 7 times 14 equals 98).
• Subtract 98 from 101 to get a remainder of 3.
• Therefore, 101 divided by 7 equals 14 with a remainder of 3.
This shows that 101 can be divided by 7, yielding a quotient of 14 and a remainder of 3.
9. Matrix Division
Matrix division is not a straightforward arithmetic operation like division with numbers; instead, it involves multiplying by the inverse of a matrix. In mathematics, to divide matrix A by matrix B, you multiply matrix A by the inverse of matrix B (that is, A times B inverse).
Example
If A is a 2x2 matrix [[2, 4], [6, 8]] and B is a 2x2 identity matrix [[1, 0], [0, 1]], find A divided by B.
• Since B is the identity matrix, B inverse is B.
• Therefore, A divided by B equals A times B inverse, which is A.
• The result is A, which is the matrix [[2, 4], [6, 8]].
This example shows that dividing by the identity matrix leaves the matrix unchanged.
10. Scalar Division
Scalar division involves dividing each element of a vector or matrix by a scalar (a single number). It is commonly used in linear algebra and vector calculus.
Example
Divide the vector [6, 9, 12] by 3.
• Divide each element by 3: [6 divided by 3, 9 divided by 3, 12 divided by 3] equals [2, 3, 4].
• The result is the vector [2, 3, 4].
This shows that dividing a vector by a scalar scales each element by that number.
1. Modulo Division
Modulo division is a type of division that returns the remainder of dividing one number by another. It is widely used in programming, cryptography, and computer science.
Example
Find 17 modulo 5.
• Divide 17 by 5 to get a quotient of 3 with a remainder of 2.
• Therefore, 17 modulo 5 equals 2.
This shows that when 17 is divided by 5, the remainder is 2.

1. Exact Division
Exact division refers to dividing numbers without leaving a remainder. In mathematics, this is known as perfect division.
Example
Divide 16 by 4.
• 4 goes into 16 exactly 4 times (since 4 times 4 equals 16).
• Thus, 16 divided by 4 equals 4, with no remainder.
This is an example of exact division where the quotient is a whole number and there is no remainder.

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## How Is Division Used in Real-world Problems?

Division is a fundamental mathematical operation that is used extensively in everyday life. It helps in understanding how quantities are distributed, rates are calculated, and comparisons are made. Here are some detailed examples of how division is applied in different real-world contexts:

#### 1. Financial Planning and Budgeting

Division is crucial in financial planning and budgeting. It is used to calculate unit prices, split bills, determine monthly savings, and manage expenses.

Example 1
Calculating Monthly Savings
Suppose you have a yearly savings goal of \$12,000. To find out how much you need to save each month to reach this goal, divide the total savings goal by the number of months in a year.

• Total savings needed \$12,000
• Number of months 12
• Monthly savings needed 12,000 ÷ 12 = \$1,000
This shows that you need to save \$1,000 per month to meet your yearly savings goal.

Example 2
Determining Cost Per Item
If you buy a pack of 6 energy drinks for \$15, you can use division to find the cost per drink.

• Total cost \$15
• Number of drinks 6
• Cost per drink 15 ÷ 6 = \$2.50
This calculation helps in comparing prices and choosing the most economical option when shopping.

Example 3
Splitting Utility Bills
If a household utility bill for electricity is \$180 and there are three roommates sharing the cost equally, division is used to determine each person's share.

• Total bill \$180
• Number of roommates 3
• Cost per roommate 180 ÷ 3 = \$60
This ensures that each roommate pays an equal share of the bill, helping to manage shared expenses fairly.

#### 2. Cooking and Recipe Adjustments

Division is often used in cooking and baking to adjust recipes according to the number of servings needed. It helps in scaling ingredients up or down proportionally.

Example 1
A recipe for pancakes serves 8 people, but you only need to make enough for 2 people. To adjust the recipe, divide each ingredient amount by 4.

• If the original recipe requires 2 cups of flour, the adjusted amount is:
2 cups ÷ 4 = 0.5 cups (or 1/2 cup)
This ensures that the recipe is accurately scaled down for fewer servings.

Example 2
Converting Measurements
If a recipe calls for 500 milliliters of water, but you only have a measuring cup marked in cups, you need to convert the measurement using division.

• 1 cup equals 250 milliliters, so divide 500 by 250 to convert to cups
500 ÷ 250 = 2 cups
This helps in using the correct amount of ingredients when converting measurements.

Example 3
Determining Portion Sizes
If you have a 2-pound roast and want to serve it in equal portions to 5 guests, divide the total weight by the number of guests.

• Total weight 2 pounds
• Number of guests 5
• Portion size per guest 2 ÷ 5 = 0.4 pounds (or 6.4 ounces)
This ensures that each guest gets an equal portion of the roast.

#### 3. Travel and Logistics

Division is commonly used in travel and logistics to calculate distances, fuel efficiency, and travel times.

Example 1
Calculating Fuel Efficiency
To determine a car's fuel efficiency, divide the number of miles driven by the number of gallons of gas used.

• If a car travels 300 miles using 10 gallons of gas, the fuel efficiency is
300 miles ÷ 10 gallons = 30 miles per gallon
This helps in estimating fuel costs and planning long trips.

Example 2
Determining Travel Time
If you are traveling a distance of 240 miles and plan to drive at an average speed of 60 miles per hour, you can use division to calculate the travel time.

• Total distance 240 miles
• Speed 60 miles per hour
• Travel time 240 ÷ 60 = 4 hours
This helps in planning departure and arrival times more accurately.

Example 3
Packing for a Trip
If you have 18 pounds of luggage and want to distribute it equally across 3 bags, divide the total weight by the number of bags.

• Total weight 18 pounds
• Number of bags 3
• Weight per bag 18 ÷ 3 = 6 pounds
This ensures that the weight is evenly distributed, making it easier to carry and complying with airline weight limits.

#### 4. Data Analysis and Statistics

Division plays a key role in data analysis and statistics, helping to calculate averages, ratios, and percentages.

Example 1
Finding the Average Score
To find the average score of 5 students who scored 80, 85, 90, 75, and 95, add the scores and divide by the number of students.

• Total score 80 + 85 + 90 + 75 + 95 = 425
• Number of students 5
• Average score 425 ÷ 5 = 85
This shows that the average score of the students is 85.

Example 2
Calculating Growth Rates
A company's revenue grew from \$500,000 to \$650,000 in a year. To find the percentage growth rate, divide the increase by the original amount and multiply by 100.

• Increase in revenue 650,000 - 500,000 = 150,000
• Growth rate (150,000 ÷ 500,000) × 100 = 30%
This calculation helps in evaluating business performance and making strategic decisions.

Example 3
Determining Market Share
If a company sells 1,200 units of a product in a market where a total of 10,000 units are sold, divide the company's sales by the total market sales to find its market share.

• Company's sales 1,200 units
• Total market sales 10,000 units
• Market share (1,200 ÷ 10,000) × 100 = 12%
This helps in understanding the company's position in the market and planning marketing strategies.

#### 5. Inventory Management

Division is essential in inventory management for calculating stock levels, reorder points, and usage rates.

Example 1
Calculating Stock Levels
A store starts with 1,200 units of a product and sells 300 units each week. To find out how many weeks the current stock will last, divide the total stock by the weekly sales.

Weeks of stock remaining 1,200 ÷ 300 = 4 weeks
This helps in planning inventory replenishments.

• Total stock 1,200 units
• Weekly sales 300 units
• Weeks of stock remaining 1,200 ÷ 300 = 4 weeks
This helps in planning inventory replenishments.

Example 2
Determining Reorder Quantity
If a warehouse reorders supplies every 2 months and uses 1,500 units of a component per month, divide the total usage by the reorder frequency to determine how much to reorder.

• Monthly usage 1,500 units
• Reorder frequency 2 months
• Reorder quantity 1,500 × 2 = 3,000 units
This ensures that the warehouse does not run out of stock between orders.

Example 3
Calculating Usage Rate
A restaurant uses 50 pounds of flour each week. If it currently has 200 pounds in stock, use division to determine how many weeks the stock will last.

• Total stock 200 pounds
• Weekly usage 50 pounds
• Weeks of stock remaining 200 ÷ 50 = 4 weeks
This helps in maintaining an adequate supply and planning future orders.

## Conclusion

Excellent work on completing this division lesson! You have developed a thorough understanding of division, a critical mathematical operation that underpins much of arithmetic and problem-solving. This lesson on division has guided you through the essential concepts of division, from basic division with whole numbers to more advanced topics such as dividing fractions, decimals, and powers.

We explored the fundamental properties of division, including non-commutativity, non-associativity, and the rules for dividing by one and itself, which are key to solving mathematical problems accurately and efficiently. You also discovered how division is applied in real-world scenarios, such as budgeting, adjusting recipes, calculating distances and travel times, analyzing data, and managing inventory.

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