Rajasthan Board RBSE Class 9 Maths Solutions Chapter 11 Area of Plane Figures Ex 11.1
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solution of the Chapter 11 Area of Plane Figures Ex 11.1. This
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Rajasthan Board RBSE Class 9 Maths Solutions Chapter 11 Area of Plane Figures Ex 11.1
Question 1.
The base and height of a triangle are 20 cm and 6 cm. Find the area of the triangle.
Solution.
Area of triangle =
× base × altitude
= × 20 × 6 = 60 cm²
The base and height of a triangle are 20 cm and 6 cm. Find the area of the triangle.
Solution.
Area of triangle =
× base × altitude=
× 20 × 6 = 60 cm²
Question 2.
Find the area of the triangle whose sides are 15 cm, 25 cm and 30 cm respectively.
Solution.
Let a = 15 cm, b = 25 cm and c = 30 cm
Find the area of the triangle whose sides are 15 cm, 25 cm and 30 cm respectively.
Solution.
Let a = 15 cm, b = 25 cm and c = 30 cm
Question 3.
Find the area of an isosceles triangle, the measure of one of its equal sides being 8 cm and the third side is 4 cm.
Solution.
Area of an isosceles triangle
Find the area of an isosceles triangle, the measure of one of its equal sides being 8 cm and the third side is 4 cm.
Solution.
Area of an isosceles triangle
Question 4.
Find the area of an equilateral triangle whose side is 20 cm.
Solution.
Area of an equilateral triangle
= 100√3 sq. cm.
Find the area of an equilateral triangle whose side is 20 cm.
Solution.
Area of an equilateral triangle
= 100√3 sq. cm.
Question 5.
A triangular plot whose two sides are 8 cm and 15 cm and its perimeter is 40 cm, then find the area of the triangular plot.
Solution.
Perimeter of triangular plot = sum of all the three sides
40 = 8 + 15 + third side
=> Third side = 40 – 23 = 17 cm
Area of triangular plot
A triangular plot whose two sides are 8 cm and 15 cm and its perimeter is 40 cm, then find the area of the triangular plot.
Solution.
Perimeter of triangular plot = sum of all the three sides
40 = 8 + 15 + third side
=> Third side = 40 – 23 = 17 cm
Area of triangular plot
Question 6.
A triangular table whose sides are in the ratio 3:4:5 and its perimeter is 36 m, then find the area of triangular table.
Solution.
Sides of table are given as 3 : 4 : 5
i.e. sides are 3x, 4x and 5x
∴Perimeter = 36 m
i.e. 3x + 4x + 5x = 36
⇒ 12x = 36
⇒ x = 3
∴Sides are 3x = 3 x 3 = 9 m
4x = 4 x 3 = 12 m
5x = 5 x 3 = 15 m
Area of triangular table
A triangular table whose sides are in the ratio 3:4:5 and its perimeter is 36 m, then find the area of triangular table.
Solution.
Sides of table are given as 3 : 4 : 5
i.e. sides are 3x, 4x and 5x
∴Perimeter = 36 m
i.e. 3x + 4x + 5x = 36
⇒ 12x = 36
⇒ x = 3
∴Sides are 3x = 3 x 3 = 9 m
4x = 4 x 3 = 12 m
5x = 5 x 3 = 15 m
Area of triangular table
Question 7.
The sides of a triangular field are 20 m, 51 m and 37 m. Find the number of flowerbeds that can be prepared if each bed is to contain 2 x 3 sq. metre space.
Solution.
Let sides of a triangular field be
a = 20 m, 6 = 51 m and c = 37 m
The sides of a triangular field are 20 m, 51 m and 37 m. Find the number of flowerbeds that can be prepared if each bed is to contain 2 x 3 sq. metre space.
Solution.
Let sides of a triangular field be
a = 20 m, 6 = 51 m and c = 37 m
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