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    Question

    The length of a rectangle is four times its breadth. If

    its length is increased by 20 cm and breadth is increased by 20 cm, the area of the rectangle is increased by 900 cm2.  Find the length of the rectangle.    
    A 40 cm. Correct Answer Incorrect Answer
    B 28 cm. Correct Answer Incorrect Answer
    C 20 cm. Correct Answer Incorrect Answer
    D 48 cm. Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let Breadth = x   and Length =  4 x ∴ Original area = 4 x × x = 4 x² Now, New Area =  ( 4 x +20 ) x (x +20)  ∴  ( 4 x +20 ) × (x +20) - 4x² = 900 ⇒ 100x=900 – 400 ⇒ x= 5 ∴ l =   4 × 5 = 20cm

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