» Summing Subtotals Only from Range

Problem:

Column A contains three groups of numbers (cells A2:A4, A7:A9, A12:A14).
Cells A5, A10 and A15 contain SUBTOTAL formulas, which total the numbers to each group.
How can we sum the subtotals values only?

Solution:

Use the SUBTOTAL function to sum each group in the range, then use the SUBTOTAL function to sum the subtotals values as shown in the following formula:
=SUBTOTAL(9,A:A)