how many product can fit inside one box? and how to find box cubic feet
Product size $= 6 \times 5$ Inches
Box size $= 10 \times 10$ inches
here's what I did so far:
$6 \times 5 = 30$ (product volume)
$10 \times 10 = 100$ (box volume)
$100 / 30 = 3$
so $3$ products can fit in this box (assume product is liquid) but if you take a look below, product is solid so only 2 can fit. i can see this in small numbers by drawing it out but how to put this in calculation, that shape is solid?

A little late probably but one can easily solve that by dividing all the dimensions of the bigger box(W, H) seperately through the corresponding dimension of the smaller box(w, h)after that round it down and then multiply the results.
(note: you eventually have to sort the dimensions)
In this case: W = 10, H = 10, w = 6, h = 5
fitW = floor(W / w) = 1
fitH = floor(H / h) = 2
result = fitW * fitH = 2 * 1 = 2
this works analogue for 3 dimensional boxes