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The length of a rectangle is twice its breadth. If its length is decreased by 5 cm and the breadth is increased by 5 cm, the area of the rectangle is increased by 75 cm2 . Therefore , the length of the rectangle is ?
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- 20 cm
- 30 cm
- 40 cm
- 50 cm
Correct Option: C
Let breadth = b, length = 2b
∴ Area of rectangle = 2b x b
= 2b2
As per question.
∵ (2b - 5 ) (b + 5 ) = 2b2 + 75
⇒ 5b = 75 + 25
⇒ 5b = 100
∴ b = 100 / 5 = 20
Hence, length of the rectangle =2b
= 2 x 20
= 40 cm.
