Question

The diameter of a circular ground is 30m . Outside it runs a path 5m wide all around. Find the area of the path​

Answer 1

Answer:

- This chapter gives all the details about the perimeter and area of plane figures. Firstly the chapter discusses squares and rectangles.

Perimeter is the distance around a closed figure whereas area is the part of the plane occupied by the closed figure.

The perimeter of the following geometrical shapes are discussed in the first section:

Square

Perimeter of a square = 4 × side

Rectangle

Perimeter of a rectangle = 2 × (length + breadth)

The section is divided into two sub-parts:

1. Triangles as parts of rectangles

2. Generalising for other congruent parts of rectangles

Before moving onto exercise 11.2, the topics Area of triangle and parallelogram are discussed.

Area of a square = side × side

Area of a rectangle = length × breadth

Area of a parallelogram = base × height

Area of a triangle =1/2 × base × height

In the other half of the chapter, circles are explained. The topic is explained in two parts:

1. Circumference of Circle

The distance around a circular region is known as its circumference.

Circumference of a circle = πd

2. Area of circle

Area of circle is given by πr2

The last part of the chapter is about the conversion of units and application of the formulas.

Based on the conversion of units for lengths, studied in the chapter, the units of areas can also be converted:

1 cm2 = 100 mm2

1 m2 = 10000 cm2

1 hectare = 10000 m2

The various formulas and the conversions of units are revised and thus their application in real life scenarios are studied in this topic. These questions require practice and thus one needs to try and solve as many questions as possible in this chapter.

Students will be briefed about important points of the chapter perimeter and area in the end.