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Working with Percents


Mike McGarry
Lesson by Mike McGarry
Magoosh Expert

Summary
Mastering percents involves understanding their application as multipliers, translating word problems into mathematical equations, and utilizing fractions for simpler calculations.
  • Percents can be converted into multipliers by changing them into their decimal form to easily calculate a percentage of a number.
  • The process of finding an unknown percentage involves setting up an equation with the percent as a variable and solving for it, translating the result back into a percentage.
  • For percents that correspond to simple fractions, such as one half or one quarter, it's sometimes more efficient to use the fraction directly in calculations.
  • Key terms in percent problems include 'is' meaning equals, 'of' meaning multiply, and replacing unknowns with variables to facilitate solving.
  • Practice problems are essential for reinforcing the concepts and methods discussed for effective learning and application.
Chapters
00:01
Percents as Multipliers
01:41
Finding an Unknown Percentage
02:17
Percents and Fractions

Solutions to the Practice Problems:

1) What is 60% of 60 

Let's translate this into a simple equation.

What --> ""x"" or what we are trying to find.

is --> ""=""

60% --> 60/100 or .6

of --> "" *"" 

x = .6 * 60

x = 36

So all we did was multiply 0.6*60 and we get 36 as our answer.

2) 52 is 40% of what number?

is --> ""=""

40% --. 40/100 or .4

of --> "" * ""

what number --> x

52 = .4 * x

We divide both sides by 0.4 and we get X = 52/0.4 = 130

Let's do a check and make sure we did everything right.

3) 18 is what percent of 45?

Before we do anything math let's do a ball park. We know that half of 45 is 22.5 So without doing any math/computation we know that 50% of 45 is 22.5 so 18 is going to be less than 50>#/p###

is --> "" =""

what percent --> x/100 

of --> ""*""

18 = (x/100) * 45

18/45 = x/100

.4 = x/100

40 = x

So 18 is 40% of 45. 

Notice we can simply divide 18 by 45 to get .4

.4 is 40% in decimal form.

4) What is 50% of 128? [64]

This one you're just dividing 128 by 2.

x = .5 * 128 or 128/2

128/2 = 64