Unable to subtract 0.1 from a number more than ten times in a row without an inaccuracy of 0.0000000000001

Question

I'm using a simple formula  =SUM(D2-$B$2)
where D2 is 100 and $B$2 is 0.1
When I keep subtracting 0.1 from the last number there is a 0.0000000000001 error after 10 subtractions
100
99.90
99.80
99.70
99.60
99.50
99.40
99.30
99.20
99.10000000000010
99.00000000000010
98.90000000000010
I know that can round the number but I'm using the spreadsheet to generate cartesian coordinates for a machine and I need to use more than this many decimal places accurately.
I'm quite suprised numbers can't do this subtraction properly as my pocket calculator can manage no sweat.
At first I thought my file was corrupted but after trying several new files and reinstalling numbers the issue persists.

Answer 1

Andrew,
The floating point processor used by Numbers calculates15 significant digits, without regard to where the decimal point falls. There can be an "error" in the last digit. If that's a problem for your purposes, you'll either have to work around it by restructuring your calculation or by resorting to an app with a more powerful math engine. For simple things like invoices, we can use the ROUND function to overcome the issue. If you actually need that much precision, you're skating on ice that's too thin with this app.
Jerry