Question
Length and breadth of a rectangular field is (x + 5) cm
and (x – 4) cm, respectively. If the cost of ploughing the field at a rate of Rs. 7 per cm² is Rs. 3087, then find the cost of fencing the field at a rate of Rs. 18 per cm.Solution
ATQ, Area of the field = 3087/7 = 441 cm² So, (x + 5)(x – 4) = 441 Or, x² + x – 441 = 0 Or, x² + 21x – 20x – 441 = 0 Or, x(x + 21) – 21(x + 21) = 0 Or, (x + 21)(x – 21) = 0 So, x = 21 Perimeter of the field = 2 × {(21 + 5) + (21 – 4)} = 86 metres Desired cost = 86 × 18 = Rs. 1548
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