CALCULATION OF AREAS. 133 



The number of roods in the '83750 of an acre may be 

 found by multiplying this by 4 and dividing by 100,000 ; 

 the number of poles, by multiplying the remaining decimal 

 by 40 and dividing by 100,000. Thus : 



83750 

 4 



3-35000 

 40 



14-00000 

 3 roods 14 poles. 



Therefore the whole area = 1 acre, 3 roods, 14 poles. 



To find the area of a triangular piece of land, find 

 the area of the triangle in square links and divide by 

 100,000. 



To find the area of a triangle in square links, multiply 

 the length of the base by the length of the perpendicular 

 from the opposite corner to the base and divide the result 

 by 2. 



Example. Find the area of the piece of land A B c. 



Set up poles at A B c. Measure B c. Travel from B 

 towards c until a point D is reached where the line A D 

 seems to be at right-angles to B c. Measure A D. 



Suppose B c = 1200 links ; A D = 168 links. 



Area in acres = 



FIG. 61. 



1200 X 161 



100000 



