Given the next example:

COLUMN A
ROW1 27.35
ROW2 112.01
ROW3 3.75
ROW4 #N/A
ROW5 4.55
ROW6 #N/A
ROW7

I want to enter a formula on cell A7 that will find all
of the cells that ARE NUMBERS, and then return the SUM
of those cells.

I asked this before, but making comparisons vs. zero or
vs. very large negative numbers does not work.

Thank you