24 Domestic Science 



17. The method used to determine the area of 

 a given figure depends to some extent upon the 

 nature of the figure. If the figure is regular or 

 symmetrical in outline a few simple measurements 

 of certain lengths in it will usually afford sufficient 

 data from which to obtain its area by easy calcu- 

 lation. The areas of certain well-known regular 

 figures may be found by calculation as described 

 below. 



(a) Area of rectangle (oblong). 



A rectangle is a four- sided rectilinear (straight- 

 lined) figure having all its angles right angles. 



(The square is a special example of a rectangle in 

 which all the sides are equal.) 



The figure ABCD in Fig. 8 is a rectangle. The side 

 AB represents 6 -00 cm., and the side EG represents 

 4*00 cm. 1 The lines drawn on the figure divide it up 

 into little squares, the sides of which represent TOO cm. 

 If we count the squares, we shall find that the total 

 number in the figure is 24. Hence the area (or quantity 

 of surface enclosed within the rectangle) is 24-0 square 

 centimetres and this number is readily obtained by 

 multiplying 4 by 6. From consideration of this and 

 similar examples, we may deduce the following simple 

 rule : 



To find the area of a rectangle, measure the lengths 

 of two adjacent sides, using the same unit of length 

 for each. Multiply together the number of units of 

 length in the one side by the number of units of length 

 in the other side. The result will be the number of 

 units of area in the rectangle, each unit being equal 



1 The actual lengths of the lines in the figure as printed are one-half 

 the values given above. All other lengths mentioned in paragraph 17 

 are reduced in like ratio. 



