Discussion
Original breadth of a rectangular box is 20 cm. The box was then remade in such a way that its length got increased by 30% but the breadth decreased by 20%. This led to an increase in area by 100sq.cm. What is the new area of the box?
Answer: C
Let the original length be \( L \), with breadth 20 cm.
\[ A_{\text{old}} = 20L \]
The length rises by 30% and the breadth falls by 20%:
\[ A_{\text{new}} = (1.3L)(0.8 \times 20) = (1.3L)(16) = 20.8L \]
\[ A_{\text{new}} - A_{\text{old}} = 0.8L = 100 \quad\Longrightarrow\quad L = 125 \text{ cm} \]
\[ A_{\text{new}} = 20.8 \times 125 = 2600 \text{ cm}^{2} \]
The question asks for the new area; the old one is 2500 cm², offered as the last distractor.
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