The edges of a triangular board are 6 cm, 8 cm and 10 cm. The cost of painting it at the rate of 9 paise per cm2 is
a = 6, b = 8, c = 10
s = (a + b + c)/2
⇒ s = (6 + 8 + 10)/2 = 24/2 = 12.
Area(Δ) = √s(s-a)(s-b)(s-c)
⇒ Area(Δ) = √12(12-6)(12-8)(12-10)
⇒ Area(Δ) = √12×6×4×2
⇒ Area(Δ) = 24cm2
Cost of painting = Area(Δ)×Cost per cm2
⇒ Cost of painting = 24×9 = 216 paise = Rs 2.16
Hence, the correct option is (B).