By what percentage does the area of a rectangle increase if each side is increased by 20%?

Problem restatementEach side of a rectangle increases by 20%. Determine the percentage increase in area.

Given data

• Original sides: L, B.
• New sides: 1.2L, 1.2B.

Concept/ApproachArea scales by the product of the side multipliers. Percentage increase = (new factor − 1) × 100%.

Step-by-Step calculationOriginal area = LBNew area = (1.2L)(1.2B) = 1.44 LBIncrease factor = 1.44 ⇒ Percentage increase = (1.44 − 1) × 100% = 44%

Verification/AlternativeUsing percentage product rule: 20% + 20% + (20% of 20%) = 40% + 4% = 44%.

Common pitfallsAdding 20% + 20% only (giving 40%) and neglecting the interaction term.

Final Answer44%