228 FARM ARITHMETIC. 



angles and rectangles by means of straight lines and pro- 

 ceed as in No. 2 and No. 1. 



4. For-a circular field : Multiply the square of the diam- 

 eter in rods by .7854 and divide by 160. 



834. I. Find the area of a field 100 rods long by 48 

 rods wide ? 



100 x 48 



Process : = 30 acres. 

 160 



835. II. Find the area of a triangular field the sides 

 of which are 20, 30, and 40 rods respectively. 



20 4- so + 40 



= 45 

 2 



45 20 = 25 



45 30 = 15 



45 40 = 5 



45 X 25_X JL5 X 5 = 84,375 



V84,375 = 290.5 

 290.5 -f- 160 = 1.81. Answer, 1.81 acres. 



836. III. Find the area of a circular field, the diam- 

 eter of which is 20 rods ? 



837. How many acres in a farm 400 rods long and 320 

 rods wide? 



838. How many acres in a triangular field the sides 

 of which are 20, 40, and 50 rods ? 



839. How many acres in a circular field the diameter 

 of which is 26 rods? 



Given the plot of a farm as shown on page 229, to find 

 its acreage. 



840. How many acres in the fields A and B together ? 



841. How many acres in the field A, assuming it to 

 be a right-angled triangle? 



