# Easy percentage prob (for pro) hahah

1. Mar 18, 2009

### geffman1

1. The problem statement, all variables and given/known data

Lithium has an average atomic weight of 6.941. If the only two stable
isotopes have mass numbers of 6.015 and 7.016, what is the natural
percent abundance of the heavier isotope?

2. Relevant equations

any help would be good. thanks ( ican do it easy when they give percent but this is different

3. The attempt at a solution

2. Mar 18, 2009

### tiny-tim

Hi geffman1!

General technique … give the answer a letter, and use that letter to get an equation.

in this case, call the proportion of the heavier isotope "x" (so the proportion of the lighter isotope is 1 - x), and write an equation.