645.1500 = ¿£645 3 0 
6. To find (p) the principal— 
(by Art. 4.) s = p (1 + in) 
dividing each side of this equation by 1 + in 
^ 1 + in 
Rule. Multiply the interest of ¿£l for one year by the number of 
years, add one to the product, and divide the amount by the sum. 
Example. B returns A ¿£645 3 0 principal and interest, for the 
loan of a sura for 5 years at 4 per cent; what was the sum advanced ? 
s = 645.15 
n — 5 
.04 
5 
.2 
1 + in = 1.2) 645.15 
s 
1 + in 
— 537.625 = ¿£537 12 6 
7. To find (n) the number of years, 
(by Art. 4) s = p + inp 
CArithmetic and Alg., 109) by transposition, inp = s — p 
dividing each side by ip, n 
V 
ip 
Rule. Multiply the interest of £l for one year by the principal, 
and divide the difference between the principal and the amount, by the 
product. 
Example. In how many years will £537 12 6 amount to £645 3 0 
at 4 per cent simple interest ? 
p — 537.625 i = 645.15 ¿=.04 
537.625 645.15 
.04 537.625 
ip = 21.50500) 
107.525(5 years 
107 525 
the 
inte: 
per 
E 
amoi 
9. 
the 
may b 
£300 
decimal 
10. Is 
it become 
The pn 
* The decimal parts of a pound corresponding to any number of shillings and 
pence may he found by referring to Table 1. 
11. To :