for some students it seems helpful to stick to a routine, a rate/unit approach ~
the cost per unit of weight or for 1 item (e.g. the cost for 500g or cost per bar)
it might also be suggested by students that you can also build up, e.g.
- for the first resource, 'margarine', you could compare the costs per 2kg
- for the second resource, 'bars', you could compare the costs for 6 bars
it is usually easier to subdivide though, e.g. for the third resource, 'trice pops', it is probably simpler to calculate prices for 100g rather than to work with (the LCM) 3000g
