SAT Math Multiple Choice Question 438: Answer and Explanation

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Question: 438

3. The Consumer Price Index (CPI) is a weighted average of the cost of certain categories of goods and services in the United States. It is one of the most widely used measures of inflation. According to the U.S. Census Bureau, the CPI was 130.7 in 1990 and was 218.1 in 2010. If the CPI continues to experience the same percent increase over the next 20 years, approximately what will the CPI be in 2030?

  • A. 145.8
  • B. 305.5
  • C. 363.9
  • D. 408.7

Correct Answer: C



Difficulty: Medium

Category: Problem Solving and Data Analysis / Rates, Ratios, Proportions, and Percentages

Strategic Advice: Find the percent increase using the formula, Then apply the same percent increase to the 2010 CPI to find the expected value in 2030.

Getting to the Answer: The amount of increase is 218.1 – 130.7 = 87.4, so the percent increase is 87.4 ÷ 130.7 = 0.6687, or 66.87% over 20 years. If the total percent increase over the next 20 years is the same, the CPI will be about 218.1 × 1.6687 = 363.9.

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