Mathematics
Grade 7
15 min
Solve percent equations
Solve percent equations
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1
Introduction & Learning Objectives
Learning Objectives
Identify the three components of a percent equation: the part, the whole, and the percent rate.
Translate real-world word problems into mathematical percent equations or proportions.
Solve for an unknown value (part, whole, or percent) in a percent equation using algebraic methods.
Accurately convert between percent, decimal, and fractional forms when solving equations.
Apply percent equations to solve practical problems involving discounts, taxes, and tips.
Evaluate the reasonableness of solutions to percent equations in context.
Ever wonder how stores calculate discounts on your favorite items? 🛍️ Or how much tip to leave for a great meal? 🍽️
In this lesson, you'll learn how to set up and solve equations involving percents. This powerful skill wil...
2
Key Concepts & Vocabulary
TermDefinitionExample
PercentA ratio that compares a number to 100. It means 'per hundred' or 'out of 100'.25% means 25 out of 100, or \frac{25}{100}.
Percent EquationA mathematical statement that shows the relationship between a part, a whole, and a percent.Part = Percent \times Whole.
PartThe amount that represents a portion or a fraction of the whole. It's often the result of taking a percent of a number.In '20 is 25% of 80', 20 is the part.
Whole (Base)The total amount, the original amount, or the entire quantity from which a part is taken.In '20 is 25% of 80', 80 is the whole.
Rate (Percent Rate)The percent value itself, which must be converted to a decimal or fraction before being used in an equation.In '20 is 25% of 80', 25% is...
3
Core Formulas
The Percent Equation (Algebraic Form)
$P = R \times W$
This formula relates the Part ($P$), the Rate ($R$, expressed as a decimal), and the Whole ($W$). Use it when you know two of the values and need to find the third.
The Percent Proportion
$\frac{P}{W} = \frac{R}{100}$
This proportion states that the ratio of the Part ($P$) to the Whole ($W$) is equal to the ratio of the Percent Rate ($R$, as a whole number percent) to 100. It's an alternative way to set up and solve percent problems.
Converting Percent to Decimal
$R_{\text{decimal}} = \frac{R_{\text{percent}}}{100}$
Before using the percent in the algebraic percent equation ($P = R \times W$), you must convert the percent to its decimal form by dividing by 100 (or moving the decimal point two places to the l...
5 more steps in this tutorial
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Challenging
In a survey, 140 people, or 35% of the total surveyed, said they prefer cats. If the survey company wants to survey a total of 600 people, how many more people do they need to survey?
A.200
B.260
C.400
D.460
Challenging
A tablet's price was reduced by 10%. During a special sale, the new price was reduced by another 20%. If the final price is $288, what was the original price of the tablet?
A.$350
B.$384
C.$400
D.$420
Challenging
A student is trying to find 85% of 120. Without calculating exactly, which of the following answers is the most reasonable?
A.141, because it's larger than 120.
B.102, because it's less than 120 but still a large portion of it.
C.18, because it's a small part of 120.
D.85, because it's the same as the percent.
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