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For more information, please see full course syllabus of Pre Algebra
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Lecture Comments (6)

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Post by Levon Guyumjan on November 27 at 08:45:17 PM

I got little bit confused a/7=9 first you said you want to multiply both sides by 7 then you end up dividing 7 with seven, why is that?

0 answers

Post by brandon smith on April 21, 2013

I just want to say thank you for all your hard work. your doing a great service math Is such an important skill to have.

Thank you and keep up the amazing work =)

1 answer

Last reply by: Professor Fung
Thu Nov 1, 2012 2:59 AM

Post by Brad Cure on October 30, 2012

Why are you doing the equation by multiplication first when we are talking about inverse operations, better to keep to your lesson's lecture structure.

1 answer

Last reply by: Jona James
Tue Sep 18, 2012 10:40 AM

Post by Jesse Ogwal on July 30, 2012

Please slow down when you are speaking.

thanks

Solving Multiplication and Division Equations

  • Use inverse operations to undo operations in the equation in order to isolate the variable. Multiplication and Division are inverse operations.
  • Division by zero is undefined. This means it is not possible to divide by zero.
  • You can use division to solve an equation by undoing multiplication. You will divide both sides of the equation by the same non-zero number and simplify.
  • You can use multiplication to solve an equation by undoing division. You will multiply both sides of the equation by the same number and simplify.

Solving Multiplication and Division Equations

Solve for x.
9x = 81
  • x = [81/9]
x = 9
Solve for y.
− 12y = 48
  • y = [48/( − 12)]
y = − 4
Solve for a.
0.7a = 1.47
  • a = [1.47/0.7]
  • a = [14.7/7]
a = 2.1
Solve for x. 105 = 7x
  • [105/7] = x
15 = x
Solve for b.
0.9b = 22.5
  • b = [22.5/0.9]
  • b = [225/9]
b = 25
Tiffany wants to buy a laptop for $ 872. How many weeks does she have to save money for if she saves $ 4 each week?
  • Let w = number of weeks.
  • $ 4w = $ 872
  • w = [$ 872/$ 4]
  • w = 218
218 weeks
[x/40] = 10
  • x = 10 ×40
x = 400
[y/0.9] = 50
  • y = 50 ×0.9
y = 45
75 = [z/2]
  • 75 ×2 = z
150 = z
There are s seats in Hung Auditorium. If the auditorium has 900 rows of seats, how many seats are in each row in terms of s ?
  • s = 900 rows × (number of seats in each row)
  • (number of seats in each row)= [s/900]
[s/900] seats

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

Solving Multiplication and Division Equations

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • What You'll Learn and Why 0:06
    • Topics Overview
  • Vocabulary 0:19
    • Division Property of Equality: Arithmetic
    • Division Property of Equality: Algebraic
    • Multiplication Property of Equality: Arithmetic
    • Multiplication Property of Equality: Algebraic
  • Vocabulary 2:49
    • Inverse Operations
  • Solve the Equation Using Division 3:09
    • Example: 8x = 56
    • Example: -6y = 42
  • Solve the Equation Using Division 4:47
    • Example: 0.9c = 1.89
  • Solve the Equation Using Division 6:11
    • Example: Saving Money
    • Example: Soccer Team
  • Solve the Equation Using Multiplication 9:56
    • Example: a/7 = 9
    • Example: t/1.7 = 6
  • Solve the Equation Using Multiplication 12:09
    • Example: y/-45 = 3.2
    • Example: -p = 14
  • Solve the Equation Using Multiplication 14:10
    • Example: Distant
  • Extra Example 1: Solve the Equation 15:58
  • Extra Example 2: Solve the Equation 17:25
  • Extra Example 3: Height of an Elephant 20:55
  • Extra Example 4: Money 23:07