Discussion
The length of a rectangle is increased by 25% and its breadth is decreased by 20%. What is the effect on its area?
Answer: A
Multiply the two factors and compare with 1.
\[ \frac{A'}{A} = (1 + 0.25)(1 - 0.20) = 1.25 \times 0.80 = 1.00 \]
The area is therefore unchanged.
The percentages look unequal but exactly offset each other, because \( \tfrac{5}{4} \times \tfrac{4}{5} = 1 \). Adding them (\( +25 - 20 = +5 \)) would suggest a 5% rise, which is the distractor.
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