insert into a Temporary table using select statement

I have my insert statement like this:

Insert into #Temp(Rownumber, Percentage) 
select RowNumber, (MFN.PercentMatch * FW.FunctionWeight)  
from dbo.MatchFirstName(@FirstName) as MFN 
  inner join dbo.FunctionWeights FW on FW.FunctionName = 'MatchFirstName'

Now, If I use only

 select RowNumber, (MFN.PercentMatch * FW.FunctionWeight)  
 from dbo.MatchFirstName(@FirstName) as MFN 
   inner join dbo.FunctionWeights FW on FW.FunctionName = 'MatchFirstName'

It gives me the correctly multiplied values but while trying to insert the multiplied values in #Temp table, it inserts value of MFN.PercentMatch only and does not multiply it with FW.FunctionWeight