What dows this formula do?
=SUM(Sheet1:Sheet4!D18)
It adds data from cell D18 of Sheet1 and cell D18 of Sheet4
It adds data form all D18 cells in Sheet1, Sheet2, Sheet3, Sheet4
It adds alla data in the range A1:D18 in Sheet1,Shee2, Shee3, and Sheet4
It adds data from cell A1 of Sheet1 and cell D18 of Sheet4