Maintain expenditure amid price rise: If the price of sugar rises by 25%, by what percentage must a family reduce consumption to keep its sugar expense unchanged?

Introduction / Context:
Another inverse-percentage adjustment: to keep spending the same when price increases, consumption must drop in the inverse ratio.

Given Data / Assumptions:

• Price increase r = 25%.
• Expenditure = Price * Quantity remains constant.

Concept / Approach:
Required decrease = r/(100 + r) * 100%.

Step-by-Step Solution:

Verification / Alternative check:
Assume initial price 100, quantity 1 ⇒ spend 100. New price 125. New quantity for same spend = 100/125 = 0.8 ⇒ 20% reduction.

Why Other Options Are Wrong:

• 21% and 22% are close but incorrect; exact math gives 20%.
• 25% would overcompensate.

Common Pitfalls:
Subtracting 25 percentage points from quantity without using the inverse ratio.

Final Answer:
20%