number of 
e sum. 
rest, for the 
advanced ? 
.37 12 6 
p + inp 
s — p 
s — p 
ip 
ir by the principal, 
the amount, by the 
amount to £645 3 0 
= .04 
years 
number of shillings and 
DISCOUNT. 
8. To find («') the rate of interest, 
(by Art. 7) inp 
dividing each side by np, i 
np 
Rule. Divide the difference between the principal and amount, by 
the product of the principal and number of years, which will give the 
interest of £\; this result, multiplied by 100, will produce the rate 
per cent. 
Example. At what rate per cent, simple interest, will £537 12 6 
amount to £645 3 in 5 years ? 
p = 537.625 s=z 645.15 n = 5 
5 537.625 
2688.125 ) 107.525 ( .04 
107.525 __100 
4 per cent. 
9. When the time is any number of years and days, or of days alone, 
the quantity n contains a fraction, the decimal corresponding to which 
may be found by Table 2; if it were required to find the amount of 
£300 in 3 years and 73 days at 5 per cent, we find by the Table the 
decimal of a year corresponding to 73 days — .2. 
n c= 3.2 p ~ 300 i 
3.2 
.05 
= .05 
in — . 160 
1. 
1 + in 
1.16 
300 
p (1 4 in) = £348 Answer. 
In many works on this subject, tables of the interest of £ l for any 
number of days are given : it is not thought necessary to insert them 
here, on account of the great facility with which they may be computed 
by the aid of Table 2: as an example, let it be required to find the 
interest of £l for 20 days at 5 per cent per annum; opposite 20 days 
in the Table is .05479452, this multiplied by .05 will give .002739726 
the interest of £l for the required time. 
DISCOUNT, 
10. Is an allowance made for the payment of a sum of money before 
it becomes due. 
The present value is the sum to be paid after deducting the discount. 
Call d — the discount, 
p — the present value, 
s = the sum due, 
n — the number of years, 
i ~ the interest of £l for one year. 
11. To find (p) the present value— 
b 2