A triangular field has two side equal as 75 m, and third one as 90 m. What is the cost of ploughing the area at the rate of ₨. 15.6/m²?

₨. 42120

s = \(\frac{a + b+ c}{2}\)

  = \(\frac{75 +75 + 90}{2}\) = 120

Area = \(\sqrt {s(s - a)(s - b)(s - c)}\)

        = \(\sqrt {120(120 - 75)(120 - 75)(120 - 90)}\)

        = \(\sqrt {120 \times 45 \times 45 \times 30}\)

        = 60 x 45 = 2700

Cost =  2700 x 15.6 = ₨. 42120