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Solve: a 3.93 = −2.86 .

a = 1.07

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Solve: n 3.47 = −2.64 .

n = 0.83

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Solve: −4.8 = 0.8 n .

Solution

We will use the Division Property of Equality.

Use the Properties of Equality to find a value for n .

.
We must divide both sides by 0.8 to isolate n . .
Simplify. .
Check: .
. .
.

Since n = −6 makes −4.8 = 0.8 n a true statement, we know we have a solution.

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Solve: −8.4 = 0.7 b .

b = −12

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Solve: −5.6 = 0.7 c .

c = −8

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Solve: p 1.8 = −6.5 .

Solution

We will use the Multiplication Property of Equality .

.
Here, p is divided by −1.8. We must multiply by −1.8 to isolate p .
Multiply. .
Check: .
. .
.

A solution to p −1.8 = −6.5 is p = 11.7 .

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Solve: c −2.6 = −4.5 .

c = 11.7

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Solve: b −1.2 = −5.4 .

b = 6.48

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Translate to an equation and solve

Now that we have solved equations with decimals, we are ready to translate word sentences to equations and solve. Remember to look for words and phrases that indicate the operations to use.

Translate and solve: The difference of n and 4.3 is 2.1 .

Solution

Translate. .
Add 4.3 to both sides of the equation. .
Simplify. .
Check: Is the difference of n and 4.3 equal to 2.1? .
Let n = 4.3 : Is the difference of 6.4 and 4.3 equal to 2.1?
Translate. .
Simplify. .
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Translate and solve: The difference of y and 4.9 is 2.8 .

y − 4.9 = 2.8; y = 7.7

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Translate and solve: The difference of z and 5.7 is 3.4 .

z − 5.7 = 3.4; z = 9.1

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Translate and solve: The product of −3.1 and x is 5.27 .

Solution

Translate. .
Divide both sides by −3.1 . .
Simplify. .
Check: Is the product of −3.1 and x equal to 5.27 ? .
Let x = −1.7 : Is the product of −3.1 and −1.7 equal to 5.27 ?
Translate. .
Simplify. .
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Translate and solve: The product of −4.3 and x is 12.04 .

−4.3 x = 12.04; x = −2.8

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Translate and solve: The product of −3.1 and m is 26.66 .

−3.1 m = 26.66; m = −8.6

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Translate and solve: The quotient of p and −2.4 is 6.5 .

Solution

Translate. .
Multiply both sides by −2.4 . .
Simplify. .
Check: Is the quotient of p and −2.4 equal to 6.5 ? .
Let p = −15.6 : Is the quotient of −15.6 and −2.4 equal to 6.5 ?
Translate. .
Simplify. .
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Translate and solve: The quotient of q and −3.4 is 4.5 .

q −3.4 = 4.5 ; q = −15.3

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Translate and solve: The quotient of r and −2.6 is 2.5 .

r −2.6 = 2.5 ; r = −6.5

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Translate and solve: The sum of n and 2.9 is 1.7 .

Solution

Translate. .
Subtract 2.9 from each side. .
Simplify. .
Check: Is the sum n and 2.9 equal to 1.7 ? .
Let n = −1.2 : Is the sum −1.2 and 2.9 equal to 1.7 ?
Translate. .
Simplify. .
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Translate and solve: The sum of j and 3.8 is 2.6 .

j + 3.8 = 2.6; j = −1.2

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Translate and solve: The sum of k and 4.7 is 0.3 .

k + 4.7 = 0.3; k = −4.4

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Key concepts

  • Determine whether a number is a solution to an equation.
    • Substitute the number for the variable in the equation.
    • Simplify the expressions on both sides of the equation.
    • Determine whether the resulting equation is true.
      If so, the number is a solution.
      If not, the number is not a solution.
  • Properties of Equality
Subtraction Property of Equality Addition Property of Equality
For any numbers a , b , and c ,
If a = b then a c = b c
For any numbers a , b , and c ,
If a = b then a + c = b + c
Division of Property of Equality Multiplication Property of Equality
For any numbers a , b , and c 0 ,
If a = b then a c = b c
For any numbers a , b , and c ,
If a = b then a c = b c

Practice makes perfect

Determine Whether a Decimal is a Solution of an Equation

In the following exercises, determine whether each number is a solution of the given equation.

x 0.8 = 2.3
x = 2 x = −1.5 x = 3.1

  1. no
  2. no
  3. yes

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y + 0.6 = −3.4
y = −4 y = −2.8 y = 2.6

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h 1.5 = −4.3
h = 6.45 h = −6.45 h = −2.1

  1. no
  2. yes
  3. no

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0.75 k = −3.6
k = −0.48 k = −4.8 k = −2.7

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Solve Equations with Decimals

In the following exercises, solve the equation.

f + 3.45 = 2.6

f = −0.85

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a + 6.2 = −1.7

a = −7.9

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c + 1.15 = −3.5

c = −4.65

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x 0.4 = −3.9

x = −3.5

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j 1.82 = −6.5

j = −4.68

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m 0.25 = −1.67

m = −1.42

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−120 = 1.5 q

q = −80

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−3.4 z = −9.18

z = 2.7

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x 0.7 = −0.4

x = −0.28

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p 5 = −1.65

p = 8.25

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r 1.2 = −6

r = 7.2

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Mixed Practice

In the following exercises, solve the equation. Then check your solution.

x 5 = −11

x = −6

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−4.2 m = −33.6

m = 8

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q + 5 6 = 1 12

q = 3 4

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2 3 = y + 3 8

y = 25 24

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11 20 = f

f = 11 20

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−4.2 a = 3.36

a = −0.8

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r 1.25 = −2.7

r = −1.45

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Translate to an Equation and Solve

In the following exercises, translate and solve.

The difference of n and 1.9 is 3.4 .

n 1.9 = 3.4 ; 5.3

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The difference n and 1.5 is 0.8 .

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The product of −6.2 and x is −4.96 .

−6.2 x = −4.96; 0.8

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The product of −4.6 and x is −3.22 .

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The quotient of y and −1.7 is −5 .

y 1.7 = −5 ; 8.5

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The quotient of z and −3.6 is 3 .

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The sum of n and −7.3 is 2.4.

n + (−7.3) = 2.4; 9.7

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The sum of n and −5.1 is 3.8 .

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Everyday math

Shawn bought a pair of shoes on sale for $78 . Solve the equation 0.75 p = 78 to find the original price of the shoes, p .

$104

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Mary bought a new refrigerator. The total price including sales tax was $1,350 . Find the retail price, r , of the refrigerator before tax by solving the equation 1.08 r = 1,350 .

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Writing exercises

Think about solving the equation 1.2 y = 60 , but do not actually solve it. Do you think the solution should be greater than 60 or less than 60 ? Explain your reasoning. Then solve the equation to see if your thinking was correct.

Answers will vary.

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Think about solving the equation 0.8 x = 200 , but do not actually solve it. Do you think the solution should be greater than 200 or less than 200 ? Explain your reasoning. Then solve the equation to see if your thinking was correct.

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Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

.

On a scale of 1–10, how would you rate your mastery of this section in light of your responses on the checklist? How can you improve this?

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
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cm
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Can you compute that for me. Ty
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what is chemistry
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what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
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chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
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you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
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can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
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"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
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Maurice
answer
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progressive wave
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fine, how about you?
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hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
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Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Prealgebra. OpenStax CNX. Jul 15, 2016 Download for free at http://legacy.cnx.org/content/col11756/1.9
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