[Kc] solving for interest rate
David Nicol
davidnicol at gmail.com
Mon Oct 20 14:33:05 PDT 2008
If anyone is considering paying in advance for Linode virtual servers,
the one-year discount is a better deal than the two-year.
$ perl r-solver12 15 24
15% discount on $24 is $20.4
a 15% discount for 24 payment at a time implies an r of 0.174889697023665
MONTH PRINCIPAL-BEFORE PAYMENT PRINCIPAL-AFTER
0 20.4000 ( 1.00) 19.4000
1 19.6848 ( 1.00) 18.6848
2 18.9591 ( 1.00) 17.9591
3 18.2228 ( 1.00) 17.2228
4 17.4756 ( 1.00) 16.4756
5 16.7175 ( 1.00) 15.7175
6 15.9482 ( 1.00) 14.9482
7 15.1677 ( 1.00) 14.1677
8 14.3757 ( 1.00) 13.3757
9 13.5721 ( 1.00) 12.5721
10 12.7566 ( 1.00) 11.7566
11 11.9292 ( 1.00) 10.9292
12 11.0897 ( 1.00) 10.0897
13 10.2378 ( 1.00) 9.2378
14 9.3734 ( 1.00) 8.3734
15 8.4963 ( 1.00) 7.4963
16 7.6064 ( 1.00) 6.6064
17 6.7034 ( 1.00) 5.7034
18 5.7871 ( 1.00) 4.7871
19 4.8574 ( 1.00) 3.8574
20 3.9140 ( 1.00) 2.9140
21 2.9568 ( 1.00) 1.9568
22 1.9855 ( 1.00) 0.9855
23 1.0000 ( 1.00) -0.0000
$ perl r-solver12 10 12
10% discount on $12 is $10.8
a 10% discount for 12 payment at a time implies an r of 0.234854609283606
MONTH PRINCIPAL-BEFORE PAYMENT PRINCIPAL-AFTER
0 10.8000 ( 1.00) 9.8000
1 9.9937 ( 1.00) 8.9937
2 9.1714 ( 1.00) 8.1714
3 8.3329 ( 1.00) 7.3329
4 7.4779 ( 1.00) 6.4779
5 6.6059 ( 1.00) 5.6059
6 5.7167 ( 1.00) 4.7167
7 4.8099 ( 1.00) 3.8099
8 3.8852 ( 1.00) 2.8852
9 2.9422 ( 1.00) 1.9422
10 1.9806 ( 1.00) 0.9806
11 1.0000 ( 1.00) 0.0000
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