COMPOUND INTEREST. 
39 
What sum ought he to require for the disposal of his title, supposing 
him to have 5 per cent interest ? 
Deducting ¿£80 from ¿£250 leaves ¿£1*70, the annuity of which we 
have to find the value— 
a = 170 i = .05 n — 20 
Table 4, 1.05" 20 = .37688948 
1 — .37688948 = .62311052 
071 
62311052 
43617736 
.05)105.928788 
2118.5757 = £2U8 H 6. 
51. Table 6 contains the present values of £l per annum, at the rates 
of 2, 2\, 3, 3i, 4, 4i, 5, 6, 7, 8, 9, and 10 per cent, for any number 
of years not exceeding 100, from which we may find the value of any 
other annuity at any of the above rates, by multiplying the value in the 
Table by the annuity of which the value is to be found. Taking the 
example above; opposite 20 years under the column of 5 per cent is 
12.462210 the present value of £l per annum for 20 years 
071 
12462210 
8723547 
£2118.5757 = the amount as before. 
What sum would be required for the purchase of an annuity of £20 
to continue 10 years, when interest of money is ¿£3 5 per cent ? 
a = 20 i — .0325 n = 10 
— log 1.0325 = 1.98610994 
n = 10 1. 
log(l-M)-"= 1.8610994 .7262721 
.2737279 = 1 — (1 +i)~ n 
20 
.0325) 5.474558 ( 168.448 = ¿£168 9 0 
325