QUALITY OF WOODS. 



275 



(3) 40 : 50-80: x and x = ~ = 100- 



KA v Of) 



(4)30:50 = 80:* % = ~~ = 133'33 ; 



oU 



as before. 



It is obvious, tbat the last mentioned method is the more 

 convenient of the two. 



ii. REDUCTION BASED UPON YIELD TABLES. 



The reduction is based upon yield tables, of which the best 

 is indicated by 1 and the others by decimals of 1. 



(a) Calculation with the Mean Quality. The mean quality is 

 obtained by multiplying the several areas by their quality 

 figures, and dividing the product by the total area. 



The reduced area of each part is obtained by calculating it 

 with the inverse proportion which exists between its own and 

 the mean quality. 



Example : as above, but let 



Quality of Block No. 1 = '6 



5> 2 = '5 



3 '4- 



, . 



== ** 



200 X - 6 + 100 X ' 



' 4 + 50 X 



Mean quality 



Beduced areas of the several blocks : 



(1) -4 : '6 = 200 :a?anda; = 2 - ' 6 = 300 acres 



-4. 



(2) -4: -5 = 100:^ x = = 125 



* 



(3) '4 : "4 = 200 : x x = = 200 



' 



(4) -4: -3 = 500:* x = ^^= 375 

 Total = 1000 acres 



