Problem-Solving and Data AnalysisHardTable showing a constant percent decrease
Problem-Solving and Data Analysis practice question
A quantity decreases by the same PERCENT each year. Which of the following tables of yearly values could show this quantity?
- A. 100, 80, 64, 51.2Correct
- B. 100, 80, 60, 40
- C. 100, 90, 70, 40
- D. 100, 50, 40, 35
Answer: A. 100, 80, 64, 51.2
A constant percent decrease means each value is the same fraction of the one before: 80/100 = 64/80 = 51.2/64 = 0.8. That is a 20% drop every year.
Why the other answers are wrong
- B. 100, 80, 60, 40
- 100, 80, 60, 40 drops by the same AMOUNT (20) each year, which is a growing percent.
- C. 100, 90, 70, 40
- The drops are 10, 20, 30 — neither a constant amount nor a constant percent.
- D. 100, 50, 40, 35
- The drops are 50, 10, 5 — the percent falls each year.
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