Or if you want to preserve your rounding until the last point in your calculations:

| Test 1 |   |   | 1:15 |  62.50 |  76 |
| Test 2 |   |   | 2:48 | 140.00 | 169 |
#+TBLFM: $5=$4*(50/60.0);Df2::$6=$4+1

Since 50/60 is 0.8333... by rounding it prematurely you lose some of the precision in your billing.
Column 6 is just there to confirm for me what org does when you add or multiply times. It counts the minutes as units and properly adjusts the hours to be 60*# of hours.

So you just have to account for that when billing

On Thu, Jul 21, 2011 at 09:37, Giovanni Ridolfi <giovanni.ridolfi@yahoo.it> wrote:
Daniel E. Doherty <ded-law@ddoherty.net> writes:

> That's certainly thinking outside the box, but I don't think it
> works.

Actually, Daniel you don't have to *think*, you've to demonstrate
that it works or that it doesn't /tertium non datur/.

> In your example, 1:09 represents 1/9th in calc's fraction mode,
> not 1+9/60 which it would have to in order to compute with it.
Not with GNU/Emacs 23.3 calc.

If you bill 50 per 1 hour, you bill

(/ 50 60.0 ) is 0.83 per minute.

If you bill 1 hour + 9 minutes it is 69 minutes

(* 0.83 69) 57.269999999999996  = 57.27

isn't it ?

And the fifth column in my table (see below) does compute 57.27 or not?

  You may say: "Ah but this is only one example, you've been lucky!"

 I reply, what about the second line?

(* (+ 120 48) 0.83) = 139.44

Calc is *really* smart, isn't it?

cheers,
Giovanni

>
> Regards,
>
> At Thu, 21 Jul 2011 13:07:28 +0200,
> Giovanni Ridolfi wrote:
>>
>> Daniel E. Doherty <ded-law@ddoherty.net> writes:
>>
>> > Hi all,
>> >
>> > I am trying to use orgmode to bill for time.  My idea is to add a column
>> > that multiplies the elapsed time column by an hourly rate.
>>
>> what about using a minute rate?
>>
>> (/ 50 60.0) 0.83 so:
>>
>> | Argo Status Hearing <2011-06-28 Tue 09:00> |   |   | 1:09 |  57.27 |
>> | Letter of Discovery Deficiencies           |   |   | 2:48 | 139.44 |
>> #+TBLFM: $5=$4*0.83;Df2
>>
>>