Area Of Plane 7th Samrala G Ldh

Area of Plane figures We have seen many solids which have flat surface (s). Look at the picture of a Slate shown on the right .The slate has a flat surface.

Any flat surface gives us an idea of a plane. The top of a table the other cover of a book or note-book and a black board gives us an idea of a plane.

A flat surface extended endlessly in all directions, is called a plane.

CONCEPT OF AREA Look at the figures given below.

Each one is a closed figure. Every closed figure encloses a certain region. The region enclosed by these figures have been shaded and shown below. The figure it self is said to be the boundary of the region.

Every region covers some surface of a plane. The measure which shows how much surface of the plane the region has covered is called the area of the region. The area of the region enclosed by a figure will in short, be referred to as the AREA OF THE FIGURE.

Unit of Area. Every measure has some unit. We know that a centimeter, a meter, a kilometer etc are units of length, a gram, a kilogram, etc are units of mass (weight), an hour, a minute, a second, etc are units of time. Area being a measure also has a unit.

Just as a ‘unit length’ is required to measure lengths and a ‘unit weight’ to measure weight, a ‘unit area’ is required to measure area. Here is a square. The length of each side is 1cm. The square is a closed figure. The area of this square is said to be one square centimeter, or 1 sq cm.

A square centimeter is a unit of area. But this unit of area is too small to measure the areas of the floors of rooms or the areas of house-plots. To measure them, We need a bigger ‘unit area’. Such a unit is the area of a square whose side is 1 meter long. The area of a square with side 1meter long is one square meter, or 1 sq m.

Finding Areas by Counting Squares We take some centimeter squared or graph papers. Then, we draw some figures on them as shown below:

4 5 1

2 6

3

Let us count the number of squares enclosed by each figure. This number gives us the area of the figure. Thus, the area of the Fig. 1 is 6 sq cm ; Fig. 2 is 8 sq cm Fig. 3 is 11 sq cm ; Fig. 4 is 9 sq cm Fig. 5 is 10 sq cm ; Fig. 6 is 8 sq cm From the above, we find that the areas of Fig.2 and Fig.6 are equal, i.e. 8 sq cm. Are these two figures exactly the same? So we can say that the two figures altogether different in shapes can have the same area.

GOVT GIRLS SR SEC SCHOOL SAMRALA (LDH) Sumandeep Kaur Kusum Lata Nazia Inderjeet Kaur Nishi

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