Class 9 Maths
Heron’s Formula
Ex.12.1 Q.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?
View Answer
Ex.12.1 Q.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.).
The advertisements yield on earning of Rs 5000 per m2 per year.
A company hired one of its walls for 3 months.
How much rent did it pay?
View Answer
Ex.12.1 Q.3
There is a slide in a park. One of its side walls has been painted in some colour with a message
“KEEP THE PARK GREEN AND CLEAN” (see Fig.).
If the sides of the wall are 15 m, 11 m and 6 m, find the area painted in colour.
View Answer
Ex.13.1 Q.4
Find the area of a triangle two sides of which are 18 cm and 10 cm and the perimeter is 42 cm.
View Answer
Ex.12.1 Q.5
Sides of a triangle are in the ratio of 12: 17: 25 and its perimeter is 540 cm. Find its area.
View Answer
Ex.12.1 Q.6
An isosceles triangle has perimeter 30 cm and each of the equal sides is 12 cm.
Find the area of the triangle.
View Answer
Ex.12.2 Q.1
A park, in the shape of a quadrilateral ABCD, has ∠C = 90°, AB = 9 m, BC = 12 m, CD = 5 m and AD = 8 m.
How much area does it occupy?
View Answer
Ex.12.2 Q.2
Find the area of a quadrilateral ABCD in which AB = 3 cm, BC = 4 cm, CD = 4 cm, DA = 5 cm and AC = 5 cm.
View Answer
Ex.12.2 Q.3
Radha made a picture of an aeroplane with coloured paper as shown in the figure.
Find the total area of the paper used.
View Answer
Ex.12.2 Q.4
A triangle and a parallelogram have the same base and the same area.
If the sides of the triangle are 26 cm, 28 cm and 30 cm and the parallelogram stands on the base 28 cm,
find the height of the parallelogram.
View Answer
Ex.12.2 Q.5
A rhombus shaped field has green grass for 18 cows to graze.
If each side of the rhombus is 30 m and its longer diagonal is 48 m,
how much area of grass field will each cow be getting?
View Answer
Ex.12.2 Q.5
An umbrella is made by stitching 10 triangular pieces of cloth of two different colours (see fig.),
each piece measuring 20 cm, 50 cm, and 50 cm. How much cloth of each colour is required for the umbrella?
View Answer
Ex.12.2 Q.7
A kite in the shape of a square with a diagonal 32 cm and an isosceles triangle of base 8 cm and sides 6 cm
each is to be made of three different shades as shown in figure.
How much paper of each shade has been used in it?
View Answer
Ex.12.2 Q.8
A floral design on a floor is made up of 16 tiles which are triangular, the sides of the triangle being 9 cm, 28 cm and 35 cm (see figure).
Find the cost of polishing the tiles at the rate of 50 p per cm2.
View Answer
Ex.12.2 Q.9
A field is in the shape of a trapezium whose parallel sides are 25 m and 10 m.
The non-parallel sides are 14 m and 13 m. Find the area of the field.
View Answer