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2.5 Prime Factorization and the Least Common Multiple

Breaking a composite number down to primes with a factor tree or ladder, then assembling those primes into the least common multiple of two numbers.

Prealgebra 2e, 2.5 Prime Factorization and the Least Common Multiple

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114 exercises

2.5 Exercise 1

Before you get started, take this readiness quiz.

Is 810810 divisible by 2,3,5,6,or10?2 , 3 , 5 , 6 , \text{or} 10 ?
If you missed this problem, review the reference.

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2.5 Exercise 2

Is 127127 prime or composite?
If you missed this problem, review the reference.

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2.5 Exercise 3

Write 2⋅2⋅2⋅22 \cdot 2 \cdot 2 \cdot 2 in exponential notation.
If you missed this problem, review the reference.

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2.5 Exercise 5

Find the prime factorization using the factor tree method: 8080

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2.5 Exercise 6

Find the prime factorization using the factor tree method: 6060

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2.5 Exercise 8

Find the prime factorization using the factor tree method: 126126

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2.5 Exercise 9

Find the prime factorization using the factor tree method: 294294

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2.5 Exercise 11

Find the prime factorization using the ladder method: 8080

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2.5 Exercise 12

Find the prime factorization using the ladder method: 6060

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2.5 Exercise 14

Find the prime factorization using the ladder method. 126126

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2.5 Exercise 15

Find the prime factorization using the ladder method. 294294

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2.5 Exercise 16

Find the LCM of 1515 and 2020 by listing multiples.

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2.5 Exercise 17

Find the least common multiple (LCM) of the given numbers: 9and129 \text{and} 12

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2.5 Exercise 18

Find the least common multiple (LCM) of the given numbers: 18and2418 \text{and} 24

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2.5 Exercise 20

Find the LCM using the prime factors method. 15and2015 \text{and} 20

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2.5 Exercise 21

Find the LCM using the prime factors method. 15and3515 \text{and} 35

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2.5 Exercise 23

Find the LCM using the prime factors method: 55,8855 , 88

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2.5 Exercise 24

Find the LCM using the prime factors method: 60,7260 , 72

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2.5 Exercise 25

Find the prime factorization of each number using the factor tree method.

8686

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2.5 Exercise 27

Find the prime factorization of each number using the factor tree method.

132132

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2.5 Exercise 29

Find the prime factorization of each number using the factor tree method.

693693

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2.5 Exercise 31

Find the prime factorization of each number using the factor tree method.

115115

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2.5 Exercise 33

Find the prime factorization of each number using the factor tree method.

24752475

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2.5 Exercise 35

Find the prime factorization of each number using the ladder method.

5656

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2.5 Exercise 37

Find the prime factorization of each number using the ladder method.

168168

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2.5 Exercise 39

Find the prime factorization of each number using the ladder method.

391391

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2.5 Exercise 41

Find the prime factorization of each number using the ladder method.

432432

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2.5 Exercise 43

Find the prime factorization of each number using the ladder method.

21602160

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2.5 Exercise 45

Find the prime factorization of each number using any method.

150150

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2.5 Exercise 47

Find the prime factorization of each number using any method.

525525

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2.5 Exercise 49

Find the prime factorization of each number using any method.

3636

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2.5 Exercise 51

Find the prime factorization of each number using any method.

350350

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2.5 Exercise 53

Find the least common multiple (LCM) by listing multiples.

8,128 , 12

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2.5 Exercise 55

Find the least common multiple (LCM) by listing multiples.

6,156 , 15

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2.5 Exercise 57

Find the least common multiple (LCM) by listing multiples.

30,4030 , 40

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2.5 Exercise 59

Find the least common multiple (LCM) by listing multiples.

60,7560 , 75

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2.5 Exercise 61

Find the least common multiple (LCM) by using the prime factors method.

8,128 , 12

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2.5 Exercise 63

Find the least common multiple (LCM) by using the prime factors method.

24,3024 , 30

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2.5 Exercise 65

Find the least common multiple (LCM) by using the prime factors method.

70,8470 , 84

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2.5 Exercise 67

Find the least common multiple (LCM) using any method.

6,216 , 21

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2.5 Exercise 69

Find the least common multiple (LCM) using any method.

24,3024 , 30

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2.5 Exercise 71

Grocery shopping Hot dogs are sold in packages of ten, but hot dog buns come in packs of eight. What is the smallest number of hot dogs and buns that can be purchased if you want to have the same number of hot dogs and buns? (Hint: it is the LCM!)

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2.5 Exercise 75

Translate from algebra to English.

3⋅83 \cdot 8

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2.5 Exercise 77

Translate from algebra to English.

24÷624 \div 6

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2.5 Exercise 79

Translate from algebra to English.

50≥4750 \geq 47

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2.5 Exercise 81

Translate from algebra to English.

n+4=13n + 4 = 13

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2.5 Exercise 83

Determine if each is an expression or equation.

5+u=845 + u = 84

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2.5 Exercise 85

Determine if each is an expression or equation.

4y−114 y - 11

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2.5 Exercise 87

Write in exponential form.

2⋅2⋅22 \cdot 2 \cdot 2

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2.5 Exercise 89

Write in exponential form.

x⋅x⋅x⋅x⋅x⋅xx \cdot x \cdot x \cdot x \cdot x \cdot x

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2.5 Exercise 91

Write in expanded form.

848^{4}

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2.5 Exercise 93

Write in expanded form.

y5y^{5}

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2.5 Exercise 95

Simplify each expression.

343^{4}

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2.5 Exercise 97

Simplify each expression.

272^{7}

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2.5 Exercise 99

Simplify.

10+2⋅510 + 2 \cdot 5

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2.5 Exercise 101

Simplify.

(30+6)÷2\left(30 + 6\right) \div 2

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2.5 Exercise 103

Simplify.

72+527^{2} + 5^{2}

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2.5 Exercise 105

Simplify.

4+3(10−1)4 + 3 \left(10 - 1\right)

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2.5 Exercise 107

Evaluate the following expressions.

9x−5whenx=79 x - 5 \text{when} x = 7

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2.5 Exercise 109

Evaluate the following expressions.

3a−4bwhena=10,b=13 a - 4 b \text{when} a = 10 , b = 1

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2.5 Exercise 111

Identify the terms in each expression.

12n2+3n+112 n^{2} + 3 n + 1

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2.5 Exercise 113

Identify the coefficient of each term.

6y6 y

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2.5 Exercise 115

Identify the like terms.

5x2,3,5y2,3x,x,45 x^{2} , 3 , 5 y^{2} , 3 x , x , 4

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2.5 Exercise 117

Simplify the following expressions by combining like terms.

15a+9a15 a + 9 a

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2.5 Exercise 119

Simplify the following expressions by combining like terms.

4x+7x+3x4 x + 7 x + 3 x

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2.5 Exercise 121

Simplify the following expressions by combining like terms.

8n+2+4n+98 n + 2 + 4 n + 9

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2.5 Exercise 123

Simplify the following expressions by combining like terms.

7y2+2y+11+3y2−87 y^{2} + 2 y + 11 + 3 y^{2} - 8

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2.5 Exercise 125

Translate the following phrases into algebraic expressions.

the difference of xx and 66

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2.5 Exercise 127

Translate the following phrases into algebraic expressions.

the product of 3n3 n and 99

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2.5 Exercise 129

Translate the following phrases into algebraic expressions.

55 times the sum of yy and 11

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2.5 Exercise 131

Translate the following phrases into algebraic expressions.

Jack bought a sandwich and a coffee. The cost of the sandwich was $3\$\text{3} more than the cost of the coffee. Call the cost of the coffee c.c . Write an expression for the cost of the sandwich.

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2.5 Exercise 133

Determine whether each number is a solution to the equation.

y+16=40y + 16 = 40

  1. ⓐ 2424
  2. ⓑ 5656

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2.5 Exercise 135

Determine whether each number is a solution to the equation.

4n+12=364 n + 12 = 36

  1. ⓐ 66
  2. ⓑ 1212

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2.5 Exercise 137

Determine whether each number is a solution to the equation.

15x−5=10x+4515 x - 5 = 10 x + 45

  1. ⓐ 22
  2. ⓑ 1010

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2.5 Exercise 141

Solve each equation using the subtraction property of equality.

c+8=14c + 8 = 14

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2.5 Exercise 143

Solve each equation using the subtraction property of equality.

23=x+1223 = x + 12

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2.5 Exercise 145

Solve each equation using the addition property of equality.

y−7=16y - 7 = 16

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2.5 Exercise 147

Solve each equation using the addition property of equality.

19=p−1519 = p - 15

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2.5 Exercise 149

Translate each English sentence into an algebraic equation.

The sum of 77 and 3333 is equal to 40.40 .

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2.5 Exercise 151

Translate each English sentence into an algebraic equation.

The product of 44 and 88 is equal to 32.32 .

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2.5 Exercise 153

Translate each English sentence into an algebraic equation.

Twice the difference of nn and 33 gives 76.76 .

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2.5 Exercise 155

Translate each English sentence into an algebraic equation and then solve it.

Eight more than xx is equal to 35.35 .

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2.5 Exercise 157

Translate each English sentence into an algebraic equation and then solve it.

The difference of qq and 1818 is 57.57 .

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2.5 Exercise 159

Solve each equation.

h−15=27h - 15 = 27

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2.5 Exercise 161

Solve each equation.

z+52=85z + 52 = 85

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2.5 Exercise 163

Solve each equation.

27=q+1927 = q + 19

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2.5 Exercise 165

Solve each equation.

31=v−2531 = v - 25

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2.5 Exercise 167

List all the multiples less than 5050 for each of the following.

33

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2.5 Exercise 169

List all the multiples less than 5050 for each of the following.

88

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2.5 Exercise 171

Using the divisibility tests, determine whether each number is divisible by 2,by3,by5,by6,and by10.2 , \text{by} 3 , \text{by} 5 , \text{by} 6 , \text{and by} 10 .

9696

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2.5 Exercise 173

Using the divisibility tests, determine whether each number is divisible by 2,by3,by5,by6,and by10.2 , \text{by} 3 , \text{by} 5 , \text{by} 6 , \text{and by} 10 .

420420

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2.5 Exercise 175

Find all the factors of each number.

3030

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2.5 Exercise 177

Find all the factors of each number.

180180

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2.5 Exercise 179

Identify each number as prime or composite.

1919

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2.5 Exercise 181

Identify each number as prime or composite.

121121

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2.5 Exercise 183

Find the prime factorization of each number.

8484

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2.5 Exercise 185

Find the prime factorization of each number.

350350

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2.5 Exercise 187

Find the least common multiple of each pair of numbers.

9,159 , 15

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2.5 Exercise 189

Find the least common multiple of each pair of numbers.

25,3525 , 35

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2.5 Exercise 191

Describe how you have used two topics from The Language of Algebra chapter in your life outside of your math class during the past month.

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2.5 Exercise 193

Translate from an algebraic equation to English phrases.

15−x15 - x

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2.5 Exercise 195

Identify each as an expression or equation.

x+6=9x + 6 = 9

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2.5 Exercise 197

Identify each as an expression or equation.

  1. ⓐ Write n⋅n⋅n⋅n⋅n⋅nn \cdot n \cdot n \cdot n \cdot n \cdot n in exponential form.
  2. ⓑ Write 353^{5} in expanded form and then simplify.

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2.5 Exercise 199

Simplify, using the order of operations.

(8+1)⋅4\left(8 + 1\right) \cdot 4

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2.5 Exercise 201

Simplify, using the order of operations.

(8+4)÷3+1\left(8 + 4\right) \div 3 + 1

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2.5 Exercise 203

Simplify, using the order of operations.

5[2+7(9−8)]5 \left[2 + 7 \left(9 - 8\right)\right]

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2.5 Exercise 205

Evaluate each expression.

y3wheny=5y^{3} \text{when} y = 5

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2.5 Exercise 207

Evaluate each expression.

hwwhenh=12,w=3h w \text{when} h = 12 , w = 3

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2.5 Exercise 209

Translate each phrase into an algebraic expression.

55 more than xx

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2.5 Exercise 211

Translate each phrase into an algebraic expression.

three times the difference of aandba \text{and} b

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2.5 Exercise 213

Solve each equation.

n−6=25n - 6 = 25

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2.5 Exercise 215

Translate each English sentence into an algebraic equation and then solve it.

1515 less than yy is 32.32 .

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2.5 Exercise 217

Translate each English sentence into an algebraic equation and then solve it.

List all the multiples of 44 that are less than 50.50 .

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2.5 Exercise 219

Translate each English sentence into an algebraic equation and then solve it.

Find the prime factorization of 1080.1080 .

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Adapted from Prealgebra 2e © 2020 Rice University. Licensed under CC BY 4.0. Source: Prealgebra 2e. Imported at revision 77a933c.