MEASUREMENT OF LAND. 47 



RULE. Find the mean breadth in rods by the foregoing 

 rule, and proceed in like manner to find the mean length 

 in rods ; then multiply the mean length by the mean 

 breadth, and divide the product by 160, and the quotient 

 will be the number of acres. 



EXAMPLE. What is the area in acres of a field of irre- 

 gular sides and ends, the various breadths of which are as 

 follows, viz. : 9, 6, 7, 8, 10 and 8 rods, and the lengths as 

 follows, viz. : 50, 40, 30 and 40 rods ? 



SOLUTION. 9 + 6 + 7 + 8 + 10 + 8=48-7-6 = 8 ro d s mean 



breadth. 

 50 + 40 + 30 + 40 = 160 -h 4 = 40 rods mean 



length. 



Then 40 x 8=320-^160=2 acres. Ans. 

 Where the field is a circle. 



RULE. Take the diameter in rods, and find the area of 

 the circle in the table of circles on page , and divide it 

 by 160, and the quotient will be the number of acres. 



EXAMPLE. What is the area in acres of a circular field 

 22 rods in diameter? 



SOLUTION. 380, area of circle, -f- 160 =2 acres and 80 

 rods, or 2|- acres. Ans. 



An acre of land is contained in a plot, 



3 by 53 rods 



4 by 40 " 



5 by 32 



7 by 22f rods 



8 by 20 " 



9 by 17| " 



10 by 16 rods 



11 by 14^ 



12 by 13 J " 



6 by 26f " 



12 rods 10 feet and 8J- inches square make an acre. 



