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The length of a room floor exceeds its breadth by 20 m. The area of the floor remains unaltered when the length is decreased by 10 m but the breadth is increased by 5 m. The area of the floor (in square metres) is :
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- 280
- 325
- 300
- 420
- 280
Correct Option: C
Let the breadth of floor be x metre.
∴ Length = (x + 20) metre
∴ Area of the floor = (x + 20) x sq. metre
According to question,
(x + 10) (x + 5) = x (x + 20)
⇒ x² + 15x + 50 = x² + 20x
20x = 15x + 50
⇒ 5x = 50
⇒ x = 10 metre
∴ Length = x + 20 = 10 + 20 = 30 metre
∴ Area of the floor = 30 × 10 = 300 sq.metre
