Question

The cost of carpeting a floor with area 120 m² is Rs 3840. What is the cost of
carpeting the floor if its area is increased by 10 m^2?
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Answer 1

$120m {}^{2} = rs.3840 \\ 130m {}^{2} = x \\ \\ 3840 \times 130 = 120x \\ 499200 = 120x \\ x = \frac{499200}{120} \\ x = 4160$