Question

If the edges of a triangular board are 15 cm, 36 cm and 39cm, then the cost of painting its one of the faces at the rate of 5 paise per cm square is

Answer 1

In the attachment I have solved this problem.

I hope that you can easily understand
solution of this problem in the attachment.

Answer 2

Hello Dear.

Here is the answer---

Given ⇒
 a = 15 cm.
 b = 36 cm.
 c = 39 cm.

Using the Heron's Formula,

 S = $\frac{a + b + c}{2}$
    = $\frac{15 + 36 + 39}{2}$
    = 90/2
    = 45

Now, 
Area of the Triangles =  $\sqrt{S(S - a)(S - b)(S - c)}$
   = $\sqrt{45(45 - 15)(45 - 36)(45 - 39)}$
   = $\sqrt{45(30)(9)(6)}$
   = $\sqrt{72900}$
   = 270 cm²

∴ Cost of Painting it = 270 × 5 Piase
    = 1350 Piase.
    = Rs. 13.5 

 
Hope it helps.