# Calculating average atomic mass

Akshath
The relative abundance of various isotopes of silicon is as Si(28) = 92.25%, Si(29) = 4.65% and Si(30) = 3.10 % . Calculate the average atomic mass of Silicon.

Ans : 28.11 u

Attempt. : I don't know how to start this problem .

ycheff
0.9225*28 + 0.0465*29 + 0.0310*30 = 28.1085

Akshath
Thanx. This holds good for all elements ( to calculate average atomic mass of Isotopes) ?

Mentor
Yes, average atomic mass is always a weighted average.