Question

The sides of a triangular board are 13cm , 14cm , and 15cm . The cost of painting it at rate of 5 per cm^2 is

Answer 1

Answer:

Rs 420

Step-by-step explanation:

Sides of Triangle = 13cm, 14cm, 15cm

A/Q

We need to find the area of the triangle first

So, Formula for area of Isoceles Triangle

= √ s(s-a)(s-b)(s-c)

where s = a+b+c/2

= 13+14+15/2

= 21

By putting 21 as S in the formula

we will get

√ 21(21-13)(21-14)(21-15)

√ 21×8×7×6

√ 7056

= 84 cm²

The cost of painting = 5 per cm²

= 5×84 cm²

= Rs 420

The cost will be Rs 420

Answer 2

Given,

The sides of the triangular board = 13 cm , 14 cm , 15 cm

Rate of painting at rate of Rs. 5 per cm².

To find,

The cost of painting.

Solution,

We can simply solve this mathematical problem by using the following mathematical process.

First of all, we have to calculate the area of the triangular board.

Here, we will be using Heron's formula.

So,

Semi-perimeter (s) = (13+14+15)/2 = 21 cm

a = 13 cm

b = 14 cm

c = 15 cm

Thus, according to the Heron's formula :

Area = √s×(s-a)×(s-b)×(s-c) = √21×(21-13)×(21-14)×(21-15) = √(21×8×7×6) = √7056 = 84 cm²

Now,

cost of 1 cm² painting = Rs. 5

cost of 84 cm² painting = (84×5) = Rs. 420

Hence, the cost of painting is Rs. 420