Gali terdiri atas isotop Ga-69 dan Ga-71, sedangkan massa atom relatif Ga adalah 69,8. Tentukan kelimpaham masing isotop galium itu .

Dimisalkan:
Ga-69 = 100-x
Ga-71 = x
Ar Ga = 69.8

Kelimpahan:
Ar = Ar1.x + Ar2.x / 100
69.8 = 69 (100-x) + 71 (x) / 100
6980 = 6900 - 69x + 71x
80 = 2x
x = 40

Ga-69
= 100-x
= 100-40
= 60%

Ga-71
= x
= 40
= 40%