There are two stable isotopes of gallium. their masses are 68.9257 amu and 70.9249 amu. If the average atomic mass of gallium is 69.73 amu, what is the natural abundance of the lighter isotope?
Note: this question is asking for the natural abundance as a decimal, not as the percent natural abundance. in otherwords, if the natural abundance was 50%, the answer would be "0.50"