Autofill referencing non-adjacent cells

Hi,

I need to calculate the volume of a frustum (cone) across a dataset given by:
wefds.png
The caveat is that I need to reference every nth cell and SUM all the values in one cell, less the tedious manual input.

For example, referencing every 3rd cell (n=3).

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I would need to do this for n=5, 10, 30 etc. and would like to know how to modify the formula accordingly.

Appreciate any help!

Not saying I'll answer this but

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but why A11 and A1 ?
Shouldn't they both be A10 ?

Also the + in the SUM should be commas.

SUM(1,2,3) not SUM(1+2+3)
SUM(1+2+3) is just 1+2+3

like

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Originally Posted by Special-K

Not saying I'll answer this but

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but why A11 and A1 ?
Shouldn't they both be A10 ?

Yes, I had made an error on my part. I have edited my original post.

Appreciate your input.

Please amend your profile to show where you are in the world. Solutions often require regional settings to be taken into account. KR - South Korea??

Will you please attach a SMALL sample Excel workbook (10-20 rows of data is usually enough)? However, please give us an indication of the approximate number of rows of data you want the solution to work with (100, 1000, 100,000 or whatever). Please don't attach a picture of an Excel sheet (no-one will want to re-type all your stuff before starting).

1. It does NOT have to be your real sheet - mock up a SAMPLE if you need to. But not 1000's of rows!!! It makes manual checking so tedious. Whatever you do... make sure that all confidential information is removed first!!

2. Make sure that your sample data are truly REPRESENTATIVE of your real data. The use of unrepresentative data is very frustrating and can lead to long delays in reaching a solution.

3. Make sure that your desired solution is also shown (mock up the results manually).

4. Try to avoid using merged cells. They cause lots of problems!

Unfortunately the attachment icon doesn't work at the moment. So, to attach an Excel file you have to do the following: Just before posting, scroll down to Go Advanced and then scroll down to Manage Attachments. Now follow the instructions at the top of that screen.

Hi Glenn,

Amended my profile and attached the file as you have advised. The sample consists of 20 rows, the real data is approximately 300 rows.
Thank you.

Hi. This is the formula that you need (hopefully!!):

Formula:

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It is an array formula. Array Formulae are a little different from ordinary formulae in that they MUST be confirmed in the FIRST CELL ONLY by pressing CTRL+SHIFT+ENTER to activate the array, not just ENTER. After that, the array can be dragged down as normal, to cover the desired range.

You will know the array is active when you see curly brackets { } - or "curly braces" for those of you in the USA, or "flower brackets" for those of you in India - appear around the outside of your formula. If you do not use CTRL+SHIFT+ENTER you will (almost always) get an error message or an incorrect answer. Press F2 on that cell and try again.

Don't type the curly brackets yourself - it won't work...

Please note that in part of the formula the ranges are staggered slightly (shown in red.

On the right of the screen is a manual calculaton to show that the formula is producing the correct paramters.

You're welcome.

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