one carton of juice is 10cm wide by 10 cm long. how many cartons of juice will fit on a refrigerator shelf that is 80 cm wide by 100 cm long?
in units of boxes, the shelf is 8 by 10. So, 80 boxes will fit.
Or, you can divide the areas: 80*100 / 10*a0 = 8000/100 = 80
If the box dimensions didn 't exactly divide the shelf dimensions, things would have to be adjusted.