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Geometry and Mensuration
The length and breadth of a rectangle are in the ratio 5:4. Find its perimeter if its area is 180 cm².
Correct answer: A
Explanation and memory cue
Let the length and breadth be 5x and 4x respectively. Area = length × breadth = 5x × 4x = 20x² = 180, so x² = 9 and x = 3. Therefore, length = 15 cm and breadth = 12 cm. Perimeter = 2 × (length + breadth) = 2 × (15 + 12) = 54 cm.