i8o 



LITHMETIC. 



quired ; and the product of ,tlie different terms, found' a^j 

 before, will give the term required, 



EXAMPLES. 



I. The first term of a geometrical series is 2, the 

 number of terms 13, and the ratio 2 j required the last 

 term. 



1, 2, 3, 4, 5, indices. 



2, 4, 8, 16, 32, leading terms. 



Then 4+4+3+2 rr index to the 13th term. 

 And 16X 16X8X413:8192 the answer. 

 In this example the indices must begin with i, and such 

 of them be chosen, as will make up the entire index to the 

 term required. 



2. Required 



Cas 



Giv. I Req. 



rls <J — — 



I- 



10. 



nls 



Solution. 



i— rX^— /. 



Lyr 



■f-I- 



axs-^ar'zzIXs-ll'""' 



^I-s Is 



Here 



a = least term. 

 / = greatest term. 

 s =: sum of all tlie terms. 

 n == number of terms. 

 r = ratio. 

 ^ L rr Logarithm. 



