The discovery of isotopes explained why some relative atomic masses are not whole numbers.
Element X has two isotopes.
The table below shows the mass numbers and percentage abundances of the isotopes of element X.
| Mass number | Percentage abundance (%) |
|---|---|
| 10 | 19.9 |
| 11 | 80.1 |
Calculate the relative atomic mass (ArA_rAr) of element X.
Give your answer to 1 decimal place.