Question

2.
The triangular side walls of a flyover have been used for advertisements. The sides of
the walls are 122 m, 22 m and 120 m (see Fig. 12.9). The advertisements yield an
earning of 5000 per mº per year. A company hired one of its walls for 3 months. How
much rent did it pay?​

Answer 1

Before, finding the answer. Let's find out on how we can find the answer.

• Here, we have to first find out the area by using the Heron's formula which is :

$\sf \sqrt{s (s-a) (s-b) (s-c)}$

Where,

S = Semi-perimeter

A = Side 1

B = Side 2

C = Side 3

• After that we must multiply the area with the cost.  

___________________

Given :

• A = 122 m
• B = 22 m
• C = 120 m
• Rate for 3 months = 5000 per m²

To find :

• Total Rent

Solution :

Semi-perimeter = $\sf \dfrac{a + b + c}{2}$

                          = $\sf \dfrac{122 + 22 + 120}{2}$

                          = $\sf \dfrac{264}{2}$

                          = 132 m

Area of Triangular side walls = $\sf \sqrt{s (s-a) (s-b) (s-c)}$

                                                = $\sf \sqrt{132 (132-122) (132-22) (132-120)}$

                                                = $\sf \sqrt{132 \times (10) \times (110) \times (12)}$

                                                = $\sf \sqrt{1742400}$

                                                = 1320 m²

∴ Area of the Wall will be 1320 m².

⇒ Then total earning will be = Total area × per m² cost.

• Total Area = 1320 m²
• 1 m² area = Rs . 5000 (Earning)

Total Earning  = 5000 × 1320

→ Rs. 66,00,000

⇒ So, further it is said that the company hired one of its walls for 3 months.  Its rent for 3 months will be :

= Total earnings × 3/12

= 66,00,000 × 3/12

→ Rs. 16,50,000