Calculating Weighted Average With Criteria

Hello,

I have a data set that looks something like the following:

Type Amount Cost
A 100 $50
A 200 $40
A 300 $35
B 250 $40
B 275 $55
B 500 $60
A 700 $20
B 350 $25
B 450 $35
C 400 $80
C 400 $60

I am having trouble creating a formula that would calculate the weighted average cost depending on the type (i.e. weighted average cost of $28.84 for A, weighted avg cost of $70 for C).

Any help anyone can provide would be greatly appreciated. Thanks.

You don't specify your XL version, assuming pre XL2007:

Weighted Average of "A"

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On an aside if you created an aggregate column for each transaction that would be be best as you could swap the SUMPRODUCT for another SUMIF where the summation range is the aggregation column.