multiplying decimals

what are

0.3 x 0.4
0.3 x 0.6
0.7 x 0.4
0.7 x 0.6 ?

and how does the diagram help?

such diagrams may well be helpful...

however, it seems that an attempt to explain decimal multiplication in terms of 'decimal places' might also benefit from an explanation involving fraction multiplication
[3 tenths x 4 tenths is 12 hundredths]

there are also possible anxieties about this model because the 'unit' shifts  from being in relation to a length (the side of the square) to a relationship with an area...

just as well that 1 x 1 is still 1...