Is this answer correct?

Question

If iodine is not present a human's diet, the thyroid gland condition called goiter develops. Iodized salt is designed to remedy this condition by providing some calcium iodate as an iodine source in normal table salt. How many atoms of iodine are provided by a 25 mg sample of table salt that contains 0.01% Ca(IO3)2

My answer came out to be 7.7e17 atoms I

Answer 1

the 0.01% is by mass.

So, of the 25mg of table salt, 0.0025 mg is the Ca(IO3)2

in grams, that is 2.5 x 10^-6 g of Ca(IO3)2

Molar mass of Ca(IO3)2 = 40 + 127 x 2 + 16 x 6 = 390 g / mol

so moles Ca(IO3)2 = 2.5 x 10^-6 / 390 = 6.4 x 10^-9 mol

molecules Ca(IO3)2 = 6.4 x 10^-9 * 6.02 x 10^23 = 3.9 x 10^15

Atoms I = Molecules x 2 = 7.7 x 10^15. Not sure why we do not agree with the power, but this is what I got.

Answer 2

(.25 mg)(1 g/1000mg)= .025 g x .01 {its the percent of salt that has a molecule that has an iodine atom} x 2 {number of iodine atoms per molecule}= .0005 g I

(.0005 g I)(1 mole I/126.9045 g I)*(6.02*10^23 molecules I/1 mole I)= 2.37186231 × 10^18 molecules iodine.

the 126.9045g/mol is the molecular weight of the iodine atom. (wikipedia)

i forgot my usual calculator in my car, so i used google calculator instead- hope it worked. included a link to the input for the second (more complicated equation)

on a side note: try to avoid using e. it can mean the 10^x power, but its easy to confuse it with the e that is the inverse of ln. if/when you are in calculus, it will make sense.
i hope i did it right.