Gujarat Board Textbook Solutions Class 9 Maths Chapter 12 Heron’s Formula Ex 12.1
Gujarat Board Textbook Solutions Class 9 Maths Chapter 12 Heron’s Formula Ex 12.1
GSEB Solutions Class 9 Maths Chapter 12 Heron’s Formula Ex 12.1
Question 1.
A traffic signal board, indicating ‘SCHOOL AHEAD’ is an equilateral triangle with side ‘a’. Find the area of the signal board, using Heron’s formula. If its perimeter is 180 cm, what will be the area of the signal board?
Solution:
According to the question, semi-perimeter of ΔABC
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. The advertisements yield an earning of ₹ 5000 per m2 per year. A company hired one of its walls for 3 months. How much rent did it pay?
Question 3.
There is a slide in a park. One of its side walls has been painted in some color with a message “KEEP THE PARK GREEN AND CLEAN”. If the sides of the wall are 15 m, 11 m, and 6 m, find the area painted in color.
Given, a = 15m, b = 11 m, c = 6m.
Question 4.
Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm.
Solution:
Given, a = 18 cm, b = 10 cm, perimeter =42 cm.
a + b + c = 42
18 + 10 + c = 42
28 + c = 42
c = 14cm
Question 5.
Sides of a triangle are in the ratio of 12: 17 : 25 and its perimeter is 540 cm. Find its area.
Solution:
Let the sides of a triangle be 12x cm, 17x cm and 25x cm.
Perimeter = 12x + 17x + 25x = 54x cm
54x = 540
x = 10
Question 6.
An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find the area of the triangle.
Solution:
Given, a = 12 cm, b = 12 cm, Perimeter = 30 cm
a + b + c = 30
12 + 12 + c = 30
c = 30 – 24 = 6cm
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