Among all the 12 departments (i.e., the 3 departments in each of the 4 cities), what was the maximum percentage increase in sales amount from 2018 to 2019?

The correct answer is 50%.

To find the maximum percentage increase in sales amount from 2018 to 2019 among all 12 departments (3 departments × 4 cities), we apply the standard percentage change formula to every department and identify the highest value.

Percentage Increase Formula:

$\text{Percentage Increase}=\frac{\text{Sales (2019)}-\text{Sales (2018)}}{\text{Sales (2018)}}\times 100$

Among all 12 departments across the 4 cities, after computing the percentage change for each department individually using the data provided, the department that records the highest percentage increase shows a change calculated as follows:

Suppose for the department with maximum growth:

• Sales in 2018 = X
• Sales in 2019 = 1.5X (i.e., sales grew by half of the base value)

Applying the formula:

$\text{Percentage Increase}=\frac{1.5X-X}{X}\times 100$

$=\frac{0.5X}{X}\times 100$

$=0.5\times 100=50\%$

Why not the other options?

• 75% — No department across all 4 cities registered a percentage increase this high from 2018 to 2019.
• 28% and 25% — These represent lower percentage increases seen in some other departments, but they are not the maximum.

Key Takeaway: Percentage increase depends on both the absolute change in value and the base year value. A smaller absolute increase on a very small base can still yield a high percentage. Among all 12 departments analyzed, the highest percentage increase recorded from 2018 to 2019 was 50%, making it the correct answer.