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    Question

    The length, breadth and height of a cuboid are 15 cm, 12

    cm and 11 cm respectively. The length is decreased by 6(2/3)%, the breadth increased by 8(1/3)%, whereas the height is kept unchanged. What is the change in the total area of the four side faces (considering the rectangle contained by the length and breadth as the base) of the cuboid?
    A Decrease by 22 cm² Correct Answer Incorrect Answer
    B Increase by 22 cm² Correct Answer Incorrect Answer
    C Increase by 33 cm² Correct Answer Incorrect Answer
    D No change Correct Answer Incorrect Answer

    Solution

    Length = 15 cm, Breadth = 12 cm, Height = 11 cm The total area of the four side faces of cuboid = 2h(l + b) The total area of the four side faces of cuboid = 22 × 27 = 594 cm2 Now, converting percentage to fraction to make calculation easy Length after decrease = 15 × 14/15 = 14 cm Breadth after increase = 12 × 13/12 = 13 cm Height (no change) = 11 cm ⇒ The total area of the four side faces after change in length and breadth = 2 × 11(14 + 13) ⇒ The total area of the four side faces after change in length and breadth = 594 cm2 ⇒ Change in total area = 594 – 594 = 0 ∴ No change in the total area of the four side faces. 

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