Checking multiple occurences and returning a different column value

Can you help please ?

Column 1 Column 2

1 0.5
2 1
3 0.5
4 1
3 1
2 1
1 1
1 1

I want formula to tell me total of column 2, dependent on the incidences of a particular number in column 1. So, for example, if looking at 1 in column 1, then formula should give me result of 2.5.

Make sense?

Thanks very much

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Thanks.

Hello and Welcome to the Forum

try this

=SUMIF($A$2:$A$9,$A2,$B$2:$B$9)

Copy and Paste the formula in a Column next to your data, assuming the data is in Column A (for 1,2,3) and Column B (for 0.5,1,0.5,)

Hope this helps