iWork Numbers formula not working

[priairefox]

I have a seemingly basic formula i am attempting for bookkeeping in a spreadsheet and cannot get it to work other than on one specific row of a spreadsheet. I attempted to do the formula in a new spreadsheet in case the previous one was corrupted or something with no luck. Basically I am trying to get a sum totalled from 3 columns into a final one to calculate a tax.

So I have attempted a SUM formula of box 1 + box 2 + box3 x 0.05. Written out like the formula would be ( (G3)+(H3)+(I3) x 0.05) which effectively should be one of 3 payment option base prices multiplying by a tax rate to give you 5% of the number. There will never be more than one number but the problem is not knowing in advance of which column I will need to take the value from to figure out the tax.

However, for a while I have had no problems only doing a sum like this from one box or column such as ( (G3) x 0.05 ) For some reason more than 2 entries to do a sum for this kind of calculation it just becomes a total of what ever number is input instead of a percentage. So when I input say 20 in a column instead of the final calculation being 1 (5% of 20) it is 20.

Hope this makes sense, I hope there is a formula work around or something I input wrong to fix this.

 

[chabig]

Your formula is wrong because you forgotabout the order of operations. Let’s say you have the three columns A, B, and C. Only one will have a value but you don’t know which one. Adding them together is the right solution:

SUM(A + B + C)

Now if you want to find the tax on that, say 5%, you multiply that sum by 0.5, like this:

Tax = 0.5 x SUM(A + B + C)

or Tax = SUM(A + B + C) x 0.5

The problem with your formula is that only multiplies column C by 0.5. Remember, muliplication is performed before the addition.

Your formula: SUM(A + B + 0.5C)

 

[priairefox]

Thank you for your input, yes I see what I did wrong now. I thought the 3 were isolated and added seperate before the calculation but they were not the way it was formulated. I tested it out with additional brackets and it works now.

Thank you

 

[ApfelKuchen]

In the examples above the "+" symbols make the use of the SUM function redundant. (C1+C2+C3)x0.05 is all you need. When using a function like SUM you'd separate each cell reference with a comma (SUM C1,C2,C3)x0.05. You've declared what math you wish to have performed on those cells when you insert the function.

Further, you can declare a range of consecutive cells such as (SUM C1:C3)x0.05 and even mix things up (SUM C1:C3,E22,F94:Z94)x0.05.

Rather than type the formula longhand, you can build the formula by clicking on the cells you want to have summed. Numbers will automatically insert the appropriate delimiter after each cell selection. The grab handles on a selected cell allow you to enlarge the selection to encompass a range of cells, or drag the selection area to encompass a different cell/cells... Lots of powerful click/drag capabilities that make creating or modifying a formula more like drawing than algebra.