class 9 math NCRT books chapter 12 heron's formula
Answers
Answer:
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Ex 12.1 Class 9 Maths 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:
Let each side of the equilateral triangle be a.
Semi-perimeter of the triangle,
NCERT Solutions for Class 9 Maths Chapter 12 Heron’s Formula Ex 12.1 Q1
Ex 12.1 Class 9 Maths 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 figure). 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?
NCERT Solutions for Class 9 Maths Chapter 12 Heron’s Formula Ex 12.1 Q2
Solution:
Let the sides of the triangular will be
a = 122m, b = 12cm, c = 22m
Semi-perimeter, s = \frac { a+b+c }{ 2 }
(\frac { 122+120+22 }{ 4 })m = \frac { 264 }{ 2 } m = 132m
The area of the triangular side wall
NCERT Solutions for Class 9 Maths Chapter 12 Heron’s Formula Ex 12.1 Q2a
Rent for 1 year (i.e. 12 months) per m2 = Rs. 5000
∴ Rent for 3 months per m2 = Rs. 5000 x \frac { 3 }{ 12 }
= Rent for 3 months for 1320 m2 = Rs
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