SCERT AP 7th Class Maths Solutions Pdf Chapter 11 Area of Plane Figures Ex 11.1 Textbook Exercise Questions and Answers.

## AP State Syllabus 7th Class Maths Solutions 11th Lesson Area of Plane Figures Ex 11.1

Question 1.

Calculate the area of the following triangles given below :

(a)

Answer:

From the figure, base = 6 cm

Height = 3 cm

Area of the triangle = \(\frac{1}{2}\) ∙ b ∙ h

= 9 sq.cm

(b)

Answer:

From the figure, base = 4.2 cm

Height = 3.2 cm

Area of the triangle = \(\frac{1}{2}\) ∙ b ∙ h

= 6.72 sq.cm

(a)

Answer:

From the figure, base = 3 cm

Height = 4 cm

Area of the triangle = \(\frac{1}{2}\) ∙ b ∙ h

= 6 sq.cm

(a)

Answer:

From the figure, base = 5 cm

Height = 2 cm

Area of the triangle = \(\frac{1}{2}\) ∙ b ∙ h

= 5 sq.cm

Question 2.

Find the area of triangle with base 3.8 cm and height 4.6 cm.

Answer:

Given base of the triangle b = 3.8 cm

Height of the triangle h = 4.6 cm

Area of the triangle = \(\frac{1}{2}\) ∙ b ∙ h

∴ Area of the triangle = 8.74 sq.cm.

Question 3.

The surface area of a triangular shape window is 24 sq.m, and height is 6m., then find the base of the triangle, if the cost of glass fitting per sqm is ₹ 250, then find total cost of glass fitting for window.

Answer:

Let,

base of the triangular window = b m

Height of the triangular window h= 6m

Area of triangular window = \(\frac{1}{2}\) ∙ b ∙ h

= 24 sq.cm

⇒ 3b = 24

⇒ b = \(\frac{24}{3}\)

= 8

∴ Base of the triangular window = 8m

Cost of glass fitting per sq.m = ₹ 250

Cost of glass fitting per 24 sq.m = 250 × 24

∴ Total cost of glass fitting for window = ₹ 6000/-

Question 4.

A traffic signal plate in the shape of triangle is having base 20 cm, height 15 cm. Find the area of the triangle. If the cost of painting is ₹ 2 per Sq.cm, then find the total cost for painting the signal board on one side.

Answer:

Given the base of the signal plate b = 20 cm

Height of the signal plate h = 15 cm

Area of the signal plate = \(\frac{1}{2}\) ∙ b ∙ h

= 150 sq.cm

∴ Area of the signal plate = 150 sq.cm

Cost of painting per sq.cm = ₹ 2

Cost of painting for 150 sq.cm = 150 × 2

∴ Total cost for painting the signal board = ₹ 300

Question 5.

find the area of triangular shaped wall painting whose base is 24m, height is 38m. Find the area of the triangle, if the cost of painting is ₹ 50 per Sq. m. and also find the total cost of painting.

Answer:

Given base of the triangular wall painting = 24 m Height = 38 m

Area of wall painting = \(\frac{1}{2}\) ∙ b ∙ h

= 456 sq.m.

Cost of painting per 1 sq.m = ₹ 50

Cost of painting for 456 sq.m = 456 × 50

∴ Total cost for painting per 456 sq.m = ₹ 22,800

Question 6.

The area of triangle shaped elevation of a house is 195 Sq.m. Its base is 26m. Find the height of elevation. Find the total cost of cementing, if the cost of cementing per Sq.m, is ₹ 250.

Answer:

Given, base of triangle shaped elevation of house b = 26 m height h = ?

Area of the triangular elevation = 195 sq.m

= \(\frac{1}{2}\) ∙ b ∙ h

⇒ 13 h = 195

Height of triangular elevation = 15 m

Cost of cementing per sq.m = ₹ 250

Cost of cementing per 195 sq.m

= 195 × 250

∴ Total cost of cementing of triangular elevation = ₹ 48,750