The sides of a rectangular field are in the ratio 3 : 4. If the area of the field is 10800 sq. m, the cost of fencing the field @ 25 paise per metre is Choose the correct choice from the following answers.
A) Rs. 55.50	B) Rs. 67.50	C) Rs. 86.50	D) Rs. 105.00	E) None of these
Solution   Let length = (3x) metres and breadth = (4x) metres.   Then, 3x × 4x = 10800 ⇔ 12x2 = 10800 ⇔ x2 =900 ⇔ x = 30.   So, length = 90 m and breadth = 120 m.   Perimeter = [2(90 + 120)] m = 420 m.   ∴ Cost of fencing = Rs. (0.25 × 420) = Rs. 105.00. Answer Rs. 105.00
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The sides of a rectangular field are in the ratio 3 : 4. If the area of the field is 10800 sq. m, the cost of fencing the field @ 25 paise per metre is