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SAT Digital Math · SL AA

Problem-Solving and Data Analysis: Percentages and Proportions

Targeted Practice Sheet 2

Worked Examples: SAT Strategy

Example 1: Easy (Successive Percentages Trap)

Question: A television is originally priced at $\$500$. The store increases the price by $20%$. A month later, the store puts the television on sale for $20%$ off the new price. What is the final price of the television?
SAT Strategy: Do not assume the price goes back to $\$500$! A $20%$ decrease on a larger number removes more value than a $20%$ increase added to a smaller number. Chain your decimal multipliers.
  1. Start with the original price: $500$.
  2. Multiply by the $20%$ increase factor ($1 + 0.20$): $500 \times 1.20 = 600$.
  3. Multiply the new price by the $20%$ decrease factor ($1 - 0.20$): $600 \times 0.80$.
  4. Calculate the final price: $480$.
  5. Answer: $480$.

Example 2: Medium (Translating "p% greater than")

Question: $210$ is $p%$ greater than $30$. What is the value of $p$?
SAT Strategy: Translate the English sentence directly into an algebraic equation using the multiplier structure: $\text{New} = \text{Original} \times (1 + \frac{p}{100})$.
  1. Set up the equation: $210 = 30(1 + \frac{p}{100})$.
  2. Divide both sides by $30$: $7 = 1 + \frac{p}{100}$.
  3. Subtract $1$ from both sides: $6 = \frac{p}{100}$.
  4. Multiply by $100$: $p = 600$.
  5. (Check: $100%$ of 30 is 30. $600%$ of 30 is 180. $30 + 180 = 210$).
  6. Answer: $600$.

Example 3: Hard (Conditional Probability in Two-Way Tables)

Question: {|l|c|c|c|} & Algebra & Geometry & Total
Juniors & 45 & 15 & 60
Seniors & 10 & 30 & 40
Total & 55 & 45 & 100
If a student is selected at random from those who take Geometry, what is the probability that the student is a Senior?
SAT Strategy: Identify the "condition." The phrase "from those who take Geometry" restricts your entire universe to the Geometry column. Ignore the rest of the table!
  1. Find the denominator: The total number of students taking Geometry is $45$.
  2. Find the numerator: Of those $45$ students, how many are Seniors? $30$.
  3. Form the probability fraction: $\frac{30}{45}$.
  4. Simplify the fraction (divide by 15): $\frac{2}{3}$.
  5. Answer: $\frac{2}{3}$.

Practice Questions

Level 1: Easy (Foundational SAT)

  1. What is $20%$ of $440$? (Grid-in)
  2. Out of $300$ seeds that were planted, $80%$ sprouted. How many of these seeds sprouted?
    • A) $24$
    • B) $80$
    • C) $240$
    • D) $280$
  3. A pair of shoes originally costs $\$80$. If the shoes are on sale for $25%$ off, what is the sale price of the shoes?
    • A) $\$20$
    • B) $\$55$
    • C) $\$60$
    • D) $\$100$
  4. In a poll of $200$ voters, $130$ voted for Candidate A and the rest voted for Candidate B. What percentage of the polled voters voted for Candidate B? (Grid-in)
  5. {|l|c|c|c|} & Right-Handed & Left-Handed & Total
    Male & 42 & 8 & 50
    Female & 45 & 5 & 50
    Total & 87 & 13 & 100
    Based on the table above, what is the probability of randomly selecting a female who is left-handed from the entire group?
    • A) $\frac{5}{100}$
    • B) $\frac{5}{50}$
    • C) $\frac{5}{13}$
    • D) $\frac{13}{100}$

Level 2: Medium (Standard SAT)

  1. A store purchases a jacket from a supplier for $\$40$. The store marks up the price by $50%$ to sell to customers. During a clearance sale, the store discounts the jacket by $20%$ off the selling price. What is the clearance price of the jacket?
    • A) $\$48$
    • B) $\$52$
    • C) $\$58$
    • D) $\$60$
  2. $72$ is $p%$ of $120$. What is the value of $p$? (Grid-in)
  3. The price of a plane ticket increased by $15%$ from March to April. If the ticket cost $\$345$ in April, what was the price of the ticket in March?
    • A) $\$293.25$
    • B) $\$300.00$
    • C) $\$330.00$
    • D) $\$396.75$
  4. {|l|c|c|c|} & Cat & Dog & Total
    Has a Yard & 12 & 38 & 50
    No Yard & 24 & 6 & 30
    Total & 36 & 44 & 80
    Based on the table, if a person who owns a dog is chosen at random, what is the probability that this person has a yard? (Grid-in)
  5. A number $x$ is increased by $25%$ to get $y$. Then, $y$ is decreased by $40%$ to get $z$. If $z = 60$, what is the value of $x$? (Grid-in)

Level 3: Hard (Advanced SAT)

  1. The regular price of a shirt at a store is $\$11.70$. The sale price of the shirt is $80%$ less than the regular price, and the sale price is $30%$ greater than the store's cost for the shirt. What was the store's cost, in dollars, for the shirt? (Grid-in)
  2. $150$ is $p%$ greater than $40$. What is the value of $p$? (Grid-in)
  3. In a company, $60%$ of the employees are female, and $40%$ are male. If $30%$ of the female employees and $25%$ of the male employees take the bus to work, what percentage of ALL employees take the bus to work?
    • A) $27.5%$
    • B) $28%$
    • C) $55%$
    • D) $58%$
  4. {|l|c|c|c|} & Passed & Failed & Total
    Studied & $x$ & 10 & 90
    Did not Study & 15 & $y$ & 60
    Total & 95 & 55 & 150
    According to the partially completed table above, what is the value of $x - y$? (Grid-in)
  5. If $a$ is $50%$ of $b$, and $b$ is $120%$ of $c$, what percentage of $c$ is $a$?
    • A) $60%$
    • B) $70%$
    • C) $170%$
    • D) $240%$

Level 4: Very Hard (Slightly beyond SAT)

  1. The price of an investment portfolio decreases by $x%$ in Year 1. In Year 2, the portfolio's new value increases by $2x%$. If the value of the portfolio at the end of Year 2 is exactly equal to its original value before Year 1, and $x > 0$, what is the value of $x$? (Grid-in)
  2. A population of a town increased by $p%$ from 2010 to 2015, and then decreased by $p%$ from 2015 to 2020. If the town's population in 2020 was $9% $ less than its population in 2010, what is the value of $p$? (Grid-in)
  3. In a certain survey, $70%$ of respondents answered "Yes" to Question 1. Of those who answered "Yes" to Question 1, $40%$ answered "Yes" to Question 2. If exactly $140$ respondents answered "Yes" to BOTH questions, how many total people responded to the survey?
    • A) 200
    • B) 350
    • C) 500
    • D) 700
  4. An electronics retailer buys a computer for $C$ dollars. The retailer marks up the price by $25%$ to create the list price. Later, the retailer offers a discount of $d%$ off the list price. If the discounted price is exactly $10%$ less than the original cost $C$, what is the value of $d$? (Grid-in)
  5. The total cost of an item, including an $8%$ sales tax, is $\$135$. A customer returns the item and receives a full refund, but the store charges a $15%$ restocking fee based on the item's price before tax. How much money, in dollars, does the store keep as a restocking fee? (Grid-in)

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