Measure with duplicates

[OliJov]

I have one table

A1   B1

A1   B2

and a child table

B1    178XX

B2    178XX

and a fact table

178XX   5

As a result I get in pivot table (this is SSAS, but ok):

A1   5

B1   5

B2   5 

but that is wrong, because the preffered answer and a correct one is

A1   10

B1   5

B2   5 

How can I do this? Measure is the simple one: sum(amount)

[Kazu]

I am not sure why your A1 and B1, B2 are shown in the same column in the pivot table when they are different fields in different entities. It might be helpful to understand better if you could show the relationships of these entities.

[OliJov]

[Kazu]

Table 3 looks like a dimension because of 1:n relationship to Table 2. At the same time it looks like a fact because you have "amount" there and you are calculating SUM. 
I guess your real fact table should be either Table 1 or Table 2 and you need to add some measures there. But since everything is dummy, nobody would be able to provide any suggestions. Giving proper name to 1, 2, 3 and A, B, R would make the troubleshooting easier.

[Kazu]

I am struggling to unserstand what these three tables are meant to be. If your measure is SUMX(Table3, Table3[amount]), 5 is the correct total (I know it is not what you want, though)

Probably your three tables are not designed in a right way. However, since your table names and column names are all dummy, I could not suggest any changes.