Mathematics
Grade 9
15 min
Multistep problems with percents
Multistep problems with percents
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1
Introduction & Learning Objectives
Learning Objectives
Deconstruct complex word problems into a sequence of individual percent calculations.
Accurately calculate the final value after applying consecutive percent increases and decreases.
Solve real-world problems involving discounts, markups, and sales tax in multiple steps.
Calculate the value of an investment after earning interest and paying a percentage-based fee.
Translate multistep percent scenarios into a single algebraic expression.
Determine the original value when given the final value after several percentage changes have occurred.
You see a $200 gaming headset with a 20% off sticker, but you also have a coupon for an additional 10% off. Is that the same as 30% off? Let's find out! 🛍️
This tutorial will guide you through solving problems that...
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Key Concepts & Vocabulary
TermDefinitionExample
Consecutive PercentsThe process of applying two or more percentage changes one after another. The key is that the base for each new percentage calculation is the result of the previous one.A stock worth $100 goes up 10% (to $110). It then drops 10%. The 10% drop is calculated from $110, not the original $100.
Percent of a PercentA calculation where you find a percentage of a value that is already a percentage of another value.Finding what 50% of 20% is. This would be 0.50 * 0.20 = 0.10, or 10%.
Base ValueThe 'whole' or original amount upon which a percentage is calculated. In multistep problems, this base value changes after each step.If an item is discounted, the original price is the first base. The discounted price then becomes the new base for calculati...
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Core Formulas
Sequential Calculation Multiplier
Final Value = Original Value * (1 ± r₁) * (1 ± r₂) * ...
Use this to chain multiple percent changes together. Use '+' for a percent increase (like tax or markup) and '-' for a percent decrease (like a discount). 'r' represents the percent rate as a decimal.
Percent Change
Percent Change = ((New Value - Original Value) / Original Value) * 100%
Use this formula to find the total percent change after multiple steps have been completed. A positive result is a percent increase, and a negative result is a percent decrease.
Simple Interest
A = P(1 + rt)
Calculates the total amount (A) in an account after 't' years with an initial principal (P) and an annual interest rate (r). This is less common in mu...
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Challenging
A computer is discounted by 20%, and then the sale price is discounted by an additional 10%. The total monetary value of the two discounts combined is $280. What was the original price of the computer?
A.$800
B.$933.33
C.$1000
D.$720
Challenging
A positive value V is increased by x% and then the new value is decreased by x%, where x is a positive number (e.g., 10%, 25%). The final value is:
A.Equal to V
B.Greater than V
C.Less than V
D.It depends on the value of V.
Challenging
An investment of $5,000 grows by 10% in the first year. A 2% fee is then charged on the new balance. In the second year, the remaining balance grows by another 8%. What is the final value of the investment after the second year's growth?
A.$5,832.00
B.$5,940.00
C.$5,713.20
D.$5,821.20
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