APPENDIX 157 



B. Tables of prolongation and discount. 



The following tables follow Kraft's in his "Zuwachsrechnun- 

 gen." Their use is best illustrated by a few examples: 



1. To find capital, Cn. 



A stand of timber has now 5,500 cubic feet per acre; a growth 

 study determines that it is growing at 2.5%. What will this stand 

 contain in 15 years, growth being assumed to continue at present 

 rate? 



Under 2.5% find figure 1.448 opposite 15 years; multiply 5,500 

 by 1.448, result is the volume per acre in 15 years. The figure 1.448 

 is I.O25 15 . 



2. To find the initial capital Co. Same stand during the last 

 10 years grew at rate of 3%. What was the volume 10 years ago? 

 Find in column of 3% the figure 1.343 opposite 10 years. Divide 

 5,500 by 1.343, result is the volume 10 years ago. 



3. To find the growth in per cent. A stand now 50 years old 

 can be sold at $6.10 per 100 cubic feet. From a growth study it is 

 evident that if kept until 70 years old the stand would bring $10 per 

 100 cubic feet. What is the per cent growth in quality these 20 



Cn 10 



years? Keeping in mind that is i.op n we have i.op 20 = = 



Co 6.10 



1.638 and p the rate of growth, 2.%. In teresting and convenient to 

 use in this connection is the fact that the capital growing at com- 



72 



pound interest doubles, approximately, every years. To illus- 



P 



trate, one dollar, or one cubic foot grows into two dollars or two 



72 



cubic feet at 3% in =-.24 years. 

 3 



