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# Excel: sum of a column, but apply a function to each cell before sum

Questions:

I have a basic excel spreadsheet like this:

```A           B           C          D       etc..
10%         219.10      34.2       6.4     etc..
6%          45.10       36.2       7.4     etc..
4%          419.10      54.2       9.4     etc..
Totals:     [SUM]       [SUM]      [SUM]   ( -- update - need totals here -- )
```

I would like to sum all the values in column B, C and D. Each cell value needs to be multiplied by the % in column A before doing the sum()

I could manually create a new column to contain the % calculation, and sum that column up, but I’m hoping to do it without the additional column.

I found this which I think is on the right track but am a little lost at implementing it.

(planning to write this calculation to an excel spreadsheet created from a php script based on values in a simple mysql database)

### EDIT

For the updated question, all you need is (in B5)

``````=SUMPRODUCT(B2:B4 * \$A2:\$A4)
``````

Copy to the right

For E2, use

``````=SUMPRODUCT(B2:D2 * \$A2)
``````

This means B2*A2 + C2*A2 + D2*A2.

But, did you know that mathematically speaking, it is the same as

``````  B2*A2 + C2*A2 + D2*A2
= A2 * (B2+C2+D2)
``````

Which is just this below?

``````=A2*SUM(B2:D2)
``````

Looking at your etc, if you need to expand it rightwards, just keep column A locked in SUMPRODUCT, or use the SUM. Example below for up to J

``````=SUMPRODUCT(B2:J2 * \$A2)
=A2*SUM(B2:J2)
``````

And copy down.