GRE General TestQuantitative ReasoningMedium
A data analyst is examining a dataset of monthly website visitors. The number of visitors increased by 20% in January compared to December. In February, the number of visitors decreased by 10% compared to January. If there were 15,000 visitors in December, how many visitors were there in February?
- A16,200
- B16,500
- C15,800
- D18,000
Show answer & explanationAnswer & explanation
Correct answer: A. 16,200
To find the number of visitors in February, we first calculate the January visitors by applying a 20% increase to December's visitors, and then apply a 10% decrease to January's visitors to get the February total.
Why the other options are wrong
- B. This option is incorrect because it incorrectly applies the percentage changes or uses the wrong base for calculation.
- C. This option is incorrect because it miscalculates the percentage decrease in February.
- D. This option is incorrect because it only calculates the January visitors without applying the February decrease.
Successive Percentage Changes
Successive percentage changes involve applying one percentage change to an initial value, and then applying a second percentage change to the new value obtained after the first change.
- Changes are applied sequentially, not cumulatively to the original value.
- An increase of x% means multiplying by (1 + x/100).
- A decrease of y% means multiplying by (1 - y/100).
Memory trick: Chain percentages, don't just add or subtract them from the start!