Final answer:
To sum the values in cell E3 across sheets Jan, Feb, and March, you would use the formula '=SUM(Jan:March!E3)'.
Step-by-step explanation:
In cell E3, to calculate the sum using a 3-D reference of the same cell (E3) from the sheets named Jan through March, you would need to use the following formula:
=SUM(Jan:March!E3)
This formula adds up the value in cell E3 across each of the sheets named Jan, Feb, and March. This ability to reference multiple sheets is a powerful feature of spreadsheet software, allowing for efficient calculations across large data sets.