258 PRACTICAL MATHEMATICS 



(2) Working with horizontal strips : 



The breadth of the strip a = 0-6 

 Then Area = 63-52 x 0-6 

 = 38-12 sq. in. 



0-6 644-6 

 ~2~ X 63-52 



= 3-045 in. 



V ox = TC x (0-6) 2 x 644-6 

 = 729-1 cub. in. 



= 430-8 inch units 



140. The Derived Figures. Let an irregular figure be enclosed 

 in a rectangle, and two adjacent sides OM and OL be taken as 

 the axes of reference (Fig. 82). 



Let P be the point where the axis OX touches the boundary 

 of the figure. 



Let the irregular area be divided into a large number of hori- 

 zontal strips each of breadth ?/. 



