in chemistry (and this is only part of it) there is SO many conversion factors you have to do
for example (just a simple example lol) calculate moles of zinc
10.8 g of Zinc x 1 mol/65.39 g = x mol of Zn
----------
there are some problems where there is like 10 converson factors (1mol/65.9 g)
----------
did i scare everyone?