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    Question

    All the four lateral walls and the ceiling of a room of

    length 10 ft, breadth 7 ft and height 5 ft are to be painted. The total cost of painting is Rs. 2724. If the cost of painting is Rs. 12 per sq ft then what is the area occupied by the doors and windows?
    A 15 sq. ft Correct Answer Incorrect Answer
    B 14 sq. ft Correct Answer Incorrect Answer
    C 13 sq. ft Correct Answer Incorrect Answer
    D 18 sq. ft Correct Answer Incorrect Answer

    Solution

    The Lateral Surface Area (LSA) = 2(l +b) ×h = 2 (10 + 7) × 5 = 170 Area of the ceiling = (l × b) = 10 × 7 = 70 Total cost = LSA + Area of ceiling – (Windows and door occupied area= x ) 2724 = (170 + 70) × 12 – x × 12 Hence, x= (2880 – 2724)/ 12 = 13 sq ft ∴ the area occupied by the doors and windows = 13 sq. ft 

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