What will be the relative atomic mass of the element A, which naturally occurs in the environment, if scientists find 612 atoms of A-15, 829 atoms of A-16, and 244 atoms of A-17?

15.78

First, you have to get the percentages of all these isotopes of Element A. Add them all up together. 612+829+244 = 1685 Then, find the percentages of each - use the formula ([Number of Atoms/Total in the Sample] x 100) ([612/1685] x 100) = 36.32% of A-15. ([829/1685] x 100) = 49.20% of A-16 ([244/1685] x 100) = 14.48% of A-17. Now do what youve always done - multiply the percentages by the masses, add them all up, and divide by 100. (36.32 x 15) + (49.20 x 16) + (14.48 x 17) /100 = 15.78