[Tutor] Calculation error with a simple program

[Steven D'Aprano]

On Sat, Dec 12, 2015 at 01:03:05AM -0600, Jim Gallaher wrote:
> Hi everyone. I'm reading through a beginners Python book and came up 
> with a super simple program. I'm not getting any errors and everything 
> runs through, but there's a logical calculation error. What the program 
> does is take an amount and calculate a couple percentages and add a 
> couple fees.
> 
> For example, if I put in a value of 1, it will output 752.12 as the sub 
> total and 753.12 as the grand total. It's off by 1 on sub total and 2 on 
> grand total.

Check your arithmetic -- with a base price of $1, the sub total is 
$752.12 and the grand total is $753.12, exactly as Python calculates.


But I wonder whether you have made a logic mistake in your code. You 
say:

dealerPrep = basePrice + 500
destinationCharge = basePrice + 250

This means that the car will cost more than TRIPLE the base price. 
Instead of $1, enter a base price of $40,000 and you will see what I 
mean: now the dealer prep is $40500 and the destination charge is 
$40250, which added to the base price gives $120750 (plus tax and 
licence). Surely that's not right, the deal charges more than the cost 
of the car for preparation? I think what you want is:

dealerPrep = 500
destinationCharge = 250



-- 
Steve