NCERT Solutions
Class 9 - Mathematics
Chapter 10: HERON’S FORMULA

Complete NCERT Solutions for problems given in HERON’S FORMULA chapter in Class 9 Mathematics.

EXERCISE 10.1

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?

Answer:

\(\dfrac{\sqrt{3}}{4} a^2\), 900, 3 cm²

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?

Answer:

₹1650000

Question. 3

There is a slide in a park. One of its side walls has been painted in some colour. If the sides of the wall are 15 m, 11 m and 6 m, find the area painted in colour.

Answer:

20√2 m²

Question. 4

Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm.

Answer:

21√11 cm²

Question. 5

Sides of a triangle are in the ratio of 12 : 17 : 25 and its perimeter is 540 cm. Find its area.

Answer:

9000 cm²

Question. 6

An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm. Find the area of the triangle.

Answer:

9√15 cm²

NCERT Solutions Class 9 – Mathematics – Chapter 10: HERON’S FORMULA | Detailed Answers