4. Compare and Order Fractions, Decimals, and Percents
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Chapter 2
4.
Compare and Order Fractions, Decimals, and Percents
This lesson delves into the fundamental skill of comparing and ordering numbers, specifically focusing on fractions, decimals, and percents. This skill is not just for academic purposes; it has practical applications in everyday life. For example, when shopping for groceries, you might need to compare prices that are listed as fractions, decimals, or percentages to get the best deal. Similarly, in finance, understanding how to order these types of numbers can help you make smarter investment choices. In the realm of data analysis, being able to compare numbers in various formats is crucial for drawing accurate conclusions. Overall, mastering this skill can significantly improve your problem-solving abilities in a wide range of situations.
Show less Show more expand_more| Student Learning Objectives: |
|---|
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| | 12 Theory slides |
| | 9 Exercises - Grade E - A |
| | Each lesson is meant to take 1-2 classroom sessions |
Compare and Order Fractions, Decimals, and Percents
Slide of 12
Numbers in different forms are often connected and need to be analyzed in comparison to each other. It is useful to know how to compare and order different forms of numbers. This topic will be covered and practiced in this lesson.
Catch-Up and Review
Here are a few recommended readings before getting started with this lesson.
Background to Help Understand Numbers
Background to Help Understand Numbers
- Whole Numbers
- Fractions
- Percents
- Forms of Rational Numbers
- Converting Between Different Forms of Numbers
- Equivalent Fractions
Background to Help Understand Multiples
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Challenge
Comparing Math Homework Progress
LaShay, Tiffaniqua, and Kevin are friends.
{"type":"choice","form":{"alts":["Tiffaniqua","LaShay","Kevin"],"noSort":true},"formTextBefore":"","formTextAfter":"","answer":2}
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Discussion
Can Any Two Numbers Be Compared?
Consider a pair of numbers. 15 % and 0.32 Which one is greater? Which is less? The first thing to check is whether the numbers have the same form. In this case, the first number is a percent and the second is a decimal number. ccc Percent & & Decimal ↓ & & ↓ 15 % & & 0.32 They do not have the same form, so they cannot be directly compared. It would be like comparing strawberries and dogs — they are just not comparable because they are too different.
It is the same way with numbers. Numbers can only be compared if they are written in the same format. cccc Percents: & 15 % & vs. & 54 % Decimals: & 0.32 & vs. & 2.19 To compare two numbers, we always begin by making sure that they have the same form. If they do, we can go ahead and compare them! If they do not, we first convert one or both numbers such that they are written in the same format.
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Discussion
Comparing Two Numbers in the Same Form
Consider two numbers in the same form. We will explore how to compare them. For example, take a look at two decimal numbers. 0.285 and 0.281 The numbers look pretty similar. To determine which is greater, compare their digits one by one moving from left to right until a greater one is found. Remember, it is important to compare the corresponding place values — tenths versus tenths, hundredths versus hundredths, and so on.
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Pop Quiz
Comparing Two Numbers in Decimal and Percent Forms
Consider the pair of numbers in different forms. Select the symbol that makes the statement true.
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Example
Ordering Decimals and Percents From Least to Greatest
Some friends are comparing their typing speeds.
a
Order their speeds from least to greatest.
{"type":"sort","form":{"alts":[{"id":0,"text":"Tiffaniqua: 254.6"},{"id":1,"text":"LaShay: 279.5"},{"id":2,"text":"Kevin: 252"}]},"formTextBefore":"","formTextAfter":"","answer":[2,0,1]}
125 %, 1.03, 98 %, 1.17 Order their results from least to greatest.
{"type":"sort","form":{"alts":[{"id":0,"text":"98 %"},{"id":1,"text":"1.03"},{"id":2,"text":"1.17"},{"id":3,"text":"125 %"}]},"formTextBefore":"","formTextAfter":"","answer":[0,1,2,3]}
Hint
a
Compare the decimal place values, digit by digit, or compare their locations on a number line.
b
Start by rewriting the numbers so that they are in the same form.
Solution
a
Let's start by considering the typing speeds of Tiffaniqua, LaShay, and Kevin in characters per minute.
Tiffaniqua:& 254.6 LaShay:& 279.5 Kevin:& 252 All these speeds are given as decimal numbers. One way to order these numbers from least to greatest is to compare them digit by digit using corresponding place values. Another method is to plot them as points on a number line. On a number line, the farther to the right the number is, the greater it is.
Notice that point K, which represents Kevin's speed, is the least because it is farthest to the left. Next comes Tiffaniqua's speed, point T. Finally, point L is the farthest to the right, meaning that LaShay's speed is the greatest. ccccc K & & T && L ↓ & &↓ && ↓ 252&<& 254.6&<&279.5 Therefore, Kevin is the slowest typist at the moment, Tiffaniqua is in the middle, and LaShay is the fastest.
b
Let's start by considering the given typing speeds. Some of them are percents and some are decimal numbers.
125 %, 1.03, 98 %, 1.17 To be able to compare the numbers, they should be written in the same form — either all as percents or all as decimal numbers. Let's rewrite the decimals as percents by multiplying them by 100 and adding the percent sign. 1.03* 100=103 % 1.17* 100=117 % Now all the numbers are written as percents! 125 %, 103 %, 98 %, 117 % We can compare the numbers by plotting them on a number line.
Finally, let's order the percents from least to greatest. cccc 98 %, & 103 %, &117 %, &125 % [0.1cm] ↓ & ↓ & ↓ & ↓ [0.1cm] 98 %, & 1.03, & 1.17, & 125 %
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Discussion
Comparing Fractions
How can we compare a pair of fractions if they have different numerators and denominators? 4/7 and 5/8 Both fractions represent a part of a whole, but it is difficult to say which one is greater straight away. The best way to compare these fractions would be to convert them to equivalent fractions that have the same denominator. 4/7 → ?/New Denom. and ?/New Denom. ← 5/8 When two fractions have the same denominator, they have a common denominator.
Concept
Common Denominator
A common denominator is a denominator that is shared between two or more fractions. Consider a few examples.
| Pair of Fractions | Common Denominator |
|---|---|
| 2/3 and 5/3 | 3 |
| 8/10 and 5/10 | 10 |
| 11/17 and 6/17 | 17 |
As an example, take a look at a pair of fractions with different denominators. 1/3 and 1/2 These fractions are in their simplest form, which means that they can only be expanded. Write the multiples of their denominators, 3 and 2, to find the factor of expansion. Multiples of3:& 3, 6, 9, 12, 15, 18, ... Multiples of2:& 2, 4, 6, 8, 10, 12, 14, ... There are two potential common denominators in these lists. Expand the first fraction by 123= 4 and the second fraction by 122= 6 to make them have a common denominator of 12. 1 * 4/3 * 4&=4/12 [1.3em] 1 * 6/2 * 6&=6/12 Now the fractions share a common denominator.
4/12 and 6/12
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Discussion
The Most Convenient Common Denominator
Fractions can have multiple common denominators, but it is usually easier to deal with smaller numbers. This is when the least common denominator comes in handy!
Concept
Least Common Denominator
The least common denominator (LCD) of two fractions is the least common multiple (LCM) of the denominators of the fractions. In other words, the least common denominator is the smallest of all the common denominators. Some examples are provided in the table below.
| Fractions | Denominators | Multiples of Denominators | Common Denominators | LCM of Denominators (LCD) |
|---|---|---|---|---|
| 2/3 and 1/2 | 3 and 2 | Multiples of3:& 3, 6, 9, 12, 15, ... Multiples of2:& 2, 4, 6, 8, 10, 12, ... | 6, 12 | 6 |
| 5/6 and 1/4 | 6 and 4 | Multiples of6:& 6, 12, 18, 24, 30, ... Multiples of4:& 4, 8, 12, 16, 20, 24, ... | 12, 24 | 12 |
| 1/4 and 5/2 | 4 and 2 | Multiples of4:& 4, 8, 12, ... Multiples of2:& 2, 4, 6, 8, 10, 12, ... | 4, 8, 12 | 4 |
To sum up, finding the least common denominator is the same as finding the least common multiple of the denominators. When fractions have a common denominator, we can compare them using their numerators.
| Fractions | 4/11 and 9/11 |
|---|---|
| Numerators | 4< 9 |
| Conclusion | 4/11<9/11 |
Extra
Comparing Fractions With Common NumeratorsSometimes two fractions share the same numerator but have different denominators. In these cases, the fractions can be compared using their denominators. Consider a pair of fractions.
5/7 and 5/16
When fractions have the same denominator, the fraction with the greater numerator is greater. However, when fractions have the same numerator but different denominators, it is the opposite — the fraction with the smaller denominator is greater.
| Same Denominator | Same Numerator |
|---|---|
| The greater numerator, the greater the fraction | The smaller denominator, the greater the fraction |
Since 7 is less than 16, the first fraction must be greater. 5/7> 5/16 To understand why this is true, think of a whole represented by 1. The denominators indicate how many pieces this whole is split into. Here, it is split into 7 pieces for the first fraction and 16 pieces for the second fraction.
Notice that the 7 pieces of the first fraction are much larger than the 16 pieces of the second. The numerator of each fraction indicates how many pieces get picked. Since the numerators are the same, 5 pieces are selected from each whole. Which fraction has a larger selected section?
The total selected area is greater in the first fraction than in the second because each of the pieces is bigger. This is why the fraction with the smaller denominator is greater if the numerators are the same.
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Pop Quiz
Comparing Two Fractions
Select the correct symbol to create a true statement. If necessary, rewrite the fractions so that they have a common denominator.
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Example
It All Started With a Ball
A local story is published in the morning newspaper.
{"type":"sort","form":{"alts":[{"id":0,"text":"5\/6"},{"id":1,"text":"2\/3"},{"id":2,"text":"5\/20"},{"id":3,"text":"1\/5"}]},"formTextBefore":"","formTextAfter":"","answer":[0,1,2,3]}
Hint
Rewrite the fractions so that they have a common denominator.
Solution
We need to order four fractions from greatest to least.
5/6, 5/20, 2/3, 1/5
They have different numerators and denominators. Let's rewrite them so that they have a common denominator so that we can compare them. Start by finding the least common multiple (LCM) of the denominators of the fractions to find a candidate for a common denominator.
Denominators 6, 20, 3, 5
First, list the multiples of all the numbers and try to find the least common one.
Multiples of6:& 6, 12, 18, ..., 54, 60, ... Multiples of20:& 20, 40, 60, 80, 100 ... Multiples of3:& 3, 6, 9, 12, ..., 57, 60 ... Multiples of5:& 5, 10, 15, 20, ..., 55, 60 ...
The LCM of the numbers is 60. Next, let's divide 60 by each of the numbers to find which factor each fraction should be expanded by.
| Denominator | Calculating the Quotient | Factor |
|---|---|---|
| 6 | 60/6 | 10 |
| 20 | 60/20 | 3 |
| 3 | 60/3 | 20 |
| 5 | 60/5 | 12 |
Now that we found the expansion factors, they can be used to rewrite the fractions into equivalent fractions with a common denominator of 60. Let's start with the first fraction of 56.
The rest of the fractions can be similarly expanded.
| Fraction | Equivalent Fraction |
|---|---|
| 5/6 | 50/60 |
| 5/20 | 15/60 |
| 2/3 | 40/60 |
| 1/5 | 12/60 |
Now we can finally compare the equivalent fractions with a common denominator ordering their numerators from greatest to least. ccccccc 50/60&> & 40/60&> &15/60&> &12/60 [0.3cm] ↓ & &↓ & & ↓ & & ↓ [0.3cm] 5/6 & &2/3 & &5/20 & &1/5
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Example
Analyzing Flower Growth
Students measured how many inches four different flowers grew in one week.
The measurements were made in different forms, which made it difficult to compare the values. Help the students by ordering the numbers from least to greatest.
{"type":"sort","form":{"alts":[{"id":0,"text":"78 %"},{"id":1,"text":"4\/5"},{"id":2,"text":"0.91"},{"id":3,"text":"1 29"}]},"formTextBefore":"","formTextAfter":"","answer":[0,1,2,3]}
Hint
Rewrite the numbers so that they are in the same form. Then, plot the numbers on a number line to help place them in order.
Solution
Let's consider the numbers of inches grown of the four different flowers. One number is a fraction, one is a decimal number, one is a mixed number, and one is a percent.
4/5, 0.91, 1 29, 78 %
To compare the numbers, they need to be written in the same form. It does not matter which format is chosen, so let's rewrite them all as percents.
Fraction
We will start by rewriting the fraction 45 as a percent. We can do this by multiplying the fraction by 100, then dividing the new numerator by the denominator. Start with the multiplication.
Now let's divide the numerator by the denominator and add a percent sign. 400/5=80 % We found that 45 corresponds to 80 %.
Decimal Number
Now let's consider the decimal number 0.91. To rewrite it as a percent, we multiply it by 100 and add a percent sign. Remember that a number can be easily multiplied by 100 by moving its decimal point two places to the right.
Finally, add a percent sign. 0.91* 100=91 %
Mixed Number
Consider the mixed number 1 29. It consists of the integer 1 and the fraction part 29. Start by rewriting the fraction part as a decimal by dividing the numerator by the denominator to two decimal places by using long division.
The fraction portion is about 0.22. Next, join the integer part of 1 and the decimal part of 0.22 to create the final decimal form of 1 29. 1 29≈ 1.22 Finally, multiply the number by 100 and add a percent sign. 1.22* 100=122 % Therefore, 1 29 corresponds to 122 %.
Comparison
Gather all the numbers and their corresponding percent forms. cccc 4/5 & 0.91 & 1 29 & 78 % ↓ & ↓ & ↓ & ↓ [0.2cm] 80 % & 91 % & 122 % & 78 % To compare the percents, we ignore the percent signs and plot the numbers on a number line.
Now we can finally order the given numbers from least to greatest. ccccccc 78 % & & 80 % & & 91 % & & 122 % [0.2cm] ↓ & & ↓ & & ↓ & & ↓ [0.2cm] 78 % & < & 4/5 & < & 0.91 & < &1 29
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Closure
Who Is Closer to Finishing Their Homework?
Earlier we considered three students and their progress with their math homework.
{"type":"choice","form":{"alts":["Tiffaniqua","LaShay","Kevin"],"noSort":true},"formTextBefore":"","formTextAfter":"","answer":2}
Solution
We want to compare the given numbers to determine who has completed the greatest amount of the homework.
60 %, 0.55, 31/50
These numbers are in different forms — a percent, a decimal number, and a fraction. The first step when comparing numbers is to have them all in the same form. Let's write all the numbers in their decimal form. We will start by dividing 60 % by 100 % to get its decimal form. 60 %/100 %=0.6
The decimal form of 60 % is 0.6. Next, let's rewrite the fraction 3150 as a decimal. We will start by converting this fraction to an equivalent fraction with a denominator of 100. Since 50* 2=100, the equivalent fraction can be found by multiplying the numerator and denominator of 3150 by 2.
31* 2/50* 2=62/100
Lastly, divide the numerator by the denominator to write the fraction as a decimal. Since the denominator is 100, the division can be performed simply by moving the decimal point of 62.0 two places to the left.
The decimal that corresponds to 3150 is 0.62. Finally, let's compare the decimal forms of the numbers. 0.6, 0.55, 0.62 We will compare the place values of each number, digit by digit, to determine the greatest number. Let's start with the pair 0.6 and 0.55. Note that 0.6 is the same as 0.60.
The decimal 0.6 is greater than 0.55. Next, let's compare 0.6 and 0.62. We will add another 0 after 6 for convenience.
The decimal 0.62 is greater than 0.6. This means that it is also greater than 0.55. 0.55 < 0.6 < 0.62 Now let's remember which initial numbers these decimals correspond to. ccccc 0.55 &< & 0.6 &< & 0.62 [0.5em] ↓ & &↓ & &↓ [0.5em] 0.55 & & 60 % & & 31/50 [0.8em] ↑ & &↑ & &↑ [0.8em] LaShay & & Tiffaniqua & & Kevin Therefore, Kevin, who has finished 3150 of the homework, has completed the greatest part of the homework.
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Compare and Order Fractions, Decimals, and Percents
Exercise 3.1
Ali has many different dreams about his future. One day he sat down and started researching about different careers, such as becoming a pilot, an astronaut, a computer programmer, and a firefighter.
He found some data about these professions but the numbers are in different forms. 5.28, 576 %, 16/3, 5 911 Order these numbers from least to greatest.
{"type":"sort","form":{"alts":[{"id":0,"text":"5.28"},{"id":1,"text":"163"},{"id":2,"text":"576 %"},{"id":3,"text":"5 911"}]},"formTextBefore":"","formTextAfter":"","answer":[0,1,2,3]}
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We are given four numbers in different forms. 5.28, 576 %, 16/3, 5 911 We can only compare them if they are in the same form. Let's rewrite all the numbers as percents, one by one.
Decimal Number
The first number 5.28 is a decimal number. Let's multiply it by 100 to convert it to a percent. We can do this by moving the decimal point two places to the right.
We need now to add the percent sign to this number. 5.28* 100=528 % As we can see, 5.28 is equivalent to 528 %.
Fraction
Now let's consider the fraction 163. First, we divide the numerator by the denominator using long division.
Next, we multiply the decimal number by 100. Also, we will add a percent sign. 5.333* 100=533.3 % We have found that 163 corresponds to about 533.3 %.
Mixed Number
Finally, consider the mixed number 5 911. We will start by rewriting it as an improper fraction using this formula. a bc=a* c+b/c Let's apply it to our mixed number.
Next, divide 64 by 11 by using the long division.
Also, multiply the decimal number by 100 and add a percent sign. 5.818* 100=581.8 % The mixed number in percent form is about 581.8 %.
Comparison
The corresponding percent forms of the numbers can now be compared to order the numbers from least to greatest. ccccccc 528 % & < & 533.3 % &< & 576 % & < & 581.8 % [0.2cm] ↓ & & ↓ & & ↓ & & ↓ [0.2cm] 5.28 & & 16/3 & & 576 % & & 5 911
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Compare and Order Fractions, Decimals, and Percents
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