GRE General TestQuantitative ReasoningMedium
A botanist is tracking the growth of a rare plant. The plant's height increases by 10% each week. If the plant is currently 20 cm tall, what will its height be after 3 weeks?
- A26.62 cm
- B26.0 cm
- C26.8 cm
- D27.2 cm
Show answer & explanationAnswer & explanation
Correct answer: A. 26.62 cm
This is a compound growth problem. After 1 week: 20 * 1.10 = 22 cm. After 2 weeks: 22 * 1.10 = 24.2 cm. After 3 weeks: 24.2 * 1.10 = 26.62 cm.
Why the other options are wrong
- B. This is a simple interest calculation (20 + 3*2 = 26), not compound growth.
- C. This is a plausible distractor, likely from a calculation error.
- D. This is a plausible distractor, likely from a calculation error.
Compound Growth
Growth that is calculated on the initial principal and also on the accumulated interest or growth from previous periods.
- Formula: P(1 + r)^n, where P is principal, r is rate, n is periods.
- Leads to exponential increase over time.
- Common in finance, biology, and population studies.
Memory trick: Principal plus rate, to the power of time, watch your growth climb!