Good morning

I need to sum the last 3 values in a range that can
contain empty cells.

A1 2.2
A2
A3 4.3
A4 1.7
A5 2.2
A6
A7 3.4
A8
A9 1.0
A10

So I need to sum 1.0, 3.4 and 2.2. The closest I've come
is a formula that sums the row numbers themselves: 9, 7, 5
and not the values in the cells.

TIA
Lisa