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A rectangle has perimeter 20 cm. If one side is x cm, the area of the rectangle is:
A20x cm²
Bx(10 − x) cm²
Cx(20 − x) cm²
D(10 − x²) cm²
Answer & Solution
Correct answer: B. x(10 − x) cm²
Perimeter = 2(length + width) = 20, so length + width = 10. If one side = x, the other = (10 − x). Area = x × (10 − x) = 10x − x² cm². Note this is a QUADRATIC polynomial, not linear — though it comes from a linear constraint.
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