How many C-13 atoms are present, on average, in a 2.1000*104-atom sample of carbon?

C-13 or Carbon-13 is an isotope of carbon that has a relative abundance of 1.109%. The other isotopes of carbon are C-12 and C-14. We use this percentage to multiply to the total atoms of carbon. The solution is as follows:

2.1*10⁴ atoms * 1.109/100 = 232.89 atoms of C-13