Martinsburg gazette. [volume] (Martinsburg, Va. [W. Va.]) 1833-1855, 1844-02-22
HOW TO CALCULATE INTEREST.
Dialogue 6etsceen Teacher and has Pupil

Teacher-What is the common rule for
acquiring INTEREST,"
Popil--Mult'ply the interest by half the
number OF months.
T.-Why do you multiply by half the
number OF months,
P-Because the principal shows the in.
terest for two months: that is the interest
of any sum for two months, or sixty DAYS,
is as many cents as dollars in the princi-
pal; to wit: SIS two months, is Is cents
interest; 1910 cents, sc. Therefore,
II is evident ifthe interest is given for two
months in the principal, it must be multi
piled by half the given number Of months
to give the true interest.
T.-How do you proceed, when the in-
terest is required for odd months, as 5. Z.
or9?
P,-For s months, multiply by 2 l-2;
for Z months, by l-2, SC.
T.-When there are days given, how do
you proceed'
P.-I multiply by one-sixth part of the
days, or take aliquot parts of the principal.
T.-Why do you multiply by one-sixth
part of the days.
because the sixth part ofthe days, is
the decimal fraction Of 60 days; that's, the
sixth part of IL days is (Which means
2 l0ths Of 60.
T.-When months and days are given,
where do you place the sixth of the days
as mul,iplier3
PAT the right hand ofthe even num-
Der of months, and point il off as deci-
NAL.
T.-What rule have you for pointing
off the product, so as to show the answer
in dollars, &c.
Pas the principal in dollars expresses
the interest in cents for two months, the
product, after multiplying by halfthe num-
Der of months. will be cents. reduce
the cents to dollars, by pointing off two
figures to the right, which are cents
those on the left are dollars. If there are
cents and mills in the principal, they are
decimals. therefore cut off as many
figures from the right (which are mills and
parts Of mills reduce those on the left as be-
fore. IL multiply by one-sixth OF the days,
cut off one more figure from the right
the sixth Of the days being decimal.
T.-When you take the aIiquot parts Of
the principal, what do you consider the
principals 5s..A
P.-The interest in cents for 60 DAYS.
T.-Do you always take the aliquot part
Of the principal as the interest for 60 DAYS.
P.-I do not. 1.-THE days are less than
six, consider the principal of mills, show
ing the interest for six days: tina. is, the
interest Of any sum for six days is as many
mills as dollars in the principal.
How do you explain this2
Pas the principal expresses the ia
terest in cents for sixty days, and as six
days is one-tenth Of sixty, and one mill
one tenth Of cent, it is evident that the
principal expresses the interest in mills
for six days, on the same priacip!e that 1t
does cents for sixty days.
T.-How do you generally cast interest
ply analysis.
T.-What is the interest of $40 for 2 |
months and 3 DAYS.
P.-The interes. of $40 for 2 months,
IS as many cents as dollars; that is 40 cents;
for three days half as many mills, that is
20-equal to 2 cents, therefore the in
terest is AZ cents.
T.-What is the interest of $50 Cor 5
months and 8 days'
P.-The interest Of $50 for 2 moaths,
Is so cents; for 4 month twice So equal
to 100 cents; for one month, halt Of so,
equal to 40 cents; 40 added to 100 equals
200 cents, the interest for months. The
interest Of $50 for 6 days, is so mills; for
for days, is half Of so equal to 40 mills;
SO mills added to 40 mills make 100 mills
equal to IL cents; IL cents added to
200 cents, make 2l2 cents-or So. ~, the
answer.