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The best thing that I can tell you is to pick one of the sheets and have all of the data on just the one. You can do this by simply referencing the data from the other sheets. For example:
In Column G you could have all the data you want to do a chart on. In G1 the formula could be ='Sheet2'!A1 and so on so that you have all of your data in this column. Then create your chart according to Column G and then hide the column.
I'm sure there are better answers out there, but this should at least get you started.