GRE General TestQuantitative ReasoningHard
A data analyst is examining a dataset of monthly website visitors. The number of visitors increased by 20% in January, then decreased by 10% in February, and finally increased by 5% in March. If there were 10,000 visitors in December (before January's increase), how many visitors were there at the end of March?
- A11,400 visitors
- B11,340 visitors
- C11,500 visitors
- D12,100 visitors
Show answer & explanationAnswer & explanation
Correct answer: B. 11,340 visitors
Apply each percentage change sequentially to the current total. Use multipliers for efficiency: (1 + increase/decrease as decimal).
Why the other options are wrong
- A. This might be a calculation error or incorrectly applying the percentages to the original amount.
- C. This might be a sum of percentages (20-10+5=15%) directly to the original amount.
- D. This would be the result if all changes were increases, or if the decrease was miscalculated.
Successive Percentage Changes
Successive percentage changes involve applying multiple percentage increases or decreases one after another, where each change is based on the value resulting from the previous change.
- Changes are applied sequentially.
- Each percentage change uses the *current* amount as its base.
- Multipliers (1 + decimal % increase, 1 - decimal % decrease) are efficient.
Memory trick: Chain Reaction Percent: Multiply by (1+change) for each step, don't revert to the start!