TABLES
For the article failing early:
ia] on].
Current Ann. Depr. = 100] Ciro (42)
For the article failing late:
soo Hi
Current Ann. Depr. = too] EE: (43)
For both articles together:
evan EI + (1 4d) ne
Current Ann. Depr. = 100: | PFE i (44)
If estimated in the ordinary way this current annual depreciation
 for the two articles would be estimated by formula (41) as
follows:
ou J2 (+l
2 dy = 100% BF: = (45
The estimate of current depreciation by formula (41) is too
small, because as will be seen by comparison of equation (43) with
equation (44):
(1 + fy trie + (1 + {perl > 2 (1 + ol (46)
"ne 1
(1 +79) GES ag > 2. (47)
By the aid of formula (40) it can in a similar fashion be shown
that the remaining value as ordinarily ascertained by such
formule is too large. In further illustration of this fact let two
identical articles of a group in the 40-year life class be compared,
one of which is doomed to fail when 30 years and the other when
50 years in service. The difference in the present value of each
$100 of investment in these two articles will be represented by
the difference in the present value of each $roo required to replace
 the one in 30 years and the present value of each $100
required to replace the other at the end of 50 years. If the actual

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or