chemistry
posted by Anonymous .
Estimate the number of atoms in 7.827 g of iron using the mass of an atomic mass unit (1.661 x 10^27). The atomic mass of Fe is 55.85 u.

You are ignoring units.
mass of iron is in grams.
atomic mass is in grams.
amu is in kg.
So you have an incompatability in units.
number atoms= massiron/(massofeach atom)
where mass ofeach atom=55.85u*mass/u
so fix the units to be compatable, and you have it. 
that is my problem i am not sure how to fix the units. Do I divide the grams by 1000 so i would have 0.007927 grams then multiply by 55.85? Thank you so much for any help.