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THE WORLD OF MATHEMATICS-III
E
EXERCISE 7.4
Look at the figure of each question carefully and answer the following
questions :
1. (a) Name the shape of the object shown in the fig.
(b) How many vertices does it have ?
(C) How many plane surfaces does it have ?
(d) How many curved surfaces does it have ?
(e) Has it any edge ?
2. (a) Name the shape of the object shown in the fig.
(b) How many edges does it have ?
(c) How many curved surfaces does it have ?
(d) How many faces does it have ?
POINT
Look at the following figures carefully.
Answers
Step-by-step explanation:
Perimeter and Area- 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.
please mark as brain list
Answer:
carefullythe following figures carefully
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