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 r 



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 1.025^'. 



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 gi-owth in quality these 20 



Cn 10 



years? Keeping in mind that is i.op" we have i.op^° = - 



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 



