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12. Herons Formula MATHEMATICS class 9 in English Medium ncert book solutions Exercise 12.1
12. Herons Formula Exercise 12.1 – Complete NCERT Book Solutions for Class 9 Mathematics (English Medium). Get all chapter explanations, extra questions, solved examples and additional practice questions for 12. Herons Formula Exercise 12.1 to help you master concepts and score higher.
12. Herons Formula MATHEMATICS class 9 in English Medium ncert book solutions Exercise 12.1
NCERT Solutions for Class 9 Mathematics play an important role in helping students understand the concepts of the chapter 12. Herons Formula clearly. This chapter includes the topic Exercise 12.1, which is essential from both academic and examination point of view. The solutions provided here are prepared strictly according to the latest NCERT syllabus and follow the guidelines of CBSE to ensure accuracy and relevance. Each question is explained in a simple and student-friendly manner so that learners can grasp the concepts without confusion. These NCERT Solutions are useful for regular study, homework help, and exam preparation. All textbook questions are solved step by step to improve problem-solving skills and conceptual clarity. Students of Class 9 studying Mathematics can use these solutions to revise important topics, understand difficult questions, and practise effectively before examinations. The chapter 12. Herons Formula is explained in a structured way, making it easier for students to connect the theory with the topic Exercise 12.1. By studying these updated NCERT Solutions for Class 9 Mathematics, students can build a strong foundation, boost their confidence, and score better marks in school and board exams.
12. Herons Formula
Exercise 12.1
Exercise 12.1
Q1. 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:
Perimeter of traffic signal board = 180 cm
Side of traffic signal board
Using equation (1), area of traffic signal board
Q2: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 Rs 5000 per m2 per year. A company hired one of its walls for 3 months. How much rent did it pay?
The sides of the triangle a,b,c are of 122 m, 22 m, and 120 m respectively.
Perimeter of triangle = (122 + 22 + 120) m
2s = 264 m
s = 132 m
By Heron's formula,
Rent of 1 m2 area per year = Rs 5000
Rent of 1 m2 area per month = Rs
Rent of 1320 m2 area for 3 months =
= Rs (5000 × 330) = Rs 1650000
Therefore, the company had to pay Rs 1650000
Q3: There is a slide in the park. One of its side walls has been painted in the same color with a message “KEEP THE PARK GREEN AND CLEAN” (see the given figure). If the sides of the wall are 15m, 11m, and 6m, find the area painted in color.
It can be observed that the area to be painted in colour is a triangle, having its sides as 11 m, 6 m, and 15 m.
Perimeter of such a triangle = (11 + 6 + 15) m
2 s = 32 m
s = 16 m
By Heron's formula
Area of triangle=
Therefore, the area painted in color is 
Q4 : Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm.
Answer :
Let the third side of the triangle be x.
Perimeter of the given triangle = 42 cm
18 cm + 10 cm + c = 42
c = 14 cm
5. Sides of a triangle are in the ratio of 12: 17: 25 and its perimeter is 540cm. Find its area of triangle.
Solution:
: Let the common ratio between the sides of the given triangle be x.
Therefore, the side of the triangle will be 12x, 17x, and 25x.
Perimeter of this triangle = 540 cm
12x + 17x + 25x = 540 cm
54x = 540 cm
x = 10 cm
Sides of the triangle will be 120 cm, 170 cm, and 250 cm.
Q6 : An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find the area of the triangle.
Solution:
Let the third side of this triangle be x.
Perimeter of triangle = 30 cm
12 cm + 12 cm + x = 30 cm
x = 6 cm
