Full resolution (JPEG) - On this page / på denna sida - Logarithms - Sinking funds and savings
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
LOGARITHMS. 85
Example.
A man 20 years old commences to save 25 cents every
working day, and places this in a savings bank at 4% interest,
computed semi-annually. How much will he have in the bank
when he is 36 years old? (Note.—25c. a day = $1.50 a
week = 26 X $1.50 = $39 in six months. 4 % per year = 2 %
per period of time ,
36 — 20 = 16 = 32 periods of time).
Solution by formula:
n _b (r« -1)
a
a
39 X (1.0232 -— 1)
1.02 — 1
39 X (1.8845 — 1)
0.02
a = 39 X 0.8845 X 50
a = 1724.775 = $1724.77 = Amount.
Thus, in 16 years a saving of 25c. a day amounts to $1724.77.
If the money is paid in advance of the first period of time
the terms will be :
a = br at the end of the first period.
a = br -f br 2
at the end of the second period.
a = br + br 2 -4- br s
at the end of the third period.
At the end of n years the last term in this geometrical
series is br a
and the first term is br, while the ratio is r. The
sum of the series is the amount, which, according to rules for
geometrical progressions (see page 69), will be
:
_ r (br n
)
— br
br (r n — 1)
a = : -
Example.
Assume that the man mentioned in previous example,
instead of commencing to save money when 20 years old,
already had $39 to put in the bank at 4 % the first period of
time, and that he always kept up paying $39 in advance semi-
annually. How much money would he then save in 16 years ?
<< prev. page << föreg. sida << >> nästa sida >> next page >>
