Question

An element is found in nature in two isotopic form with mass number (A - 1) and (A + 1). If the average atomic mass of the element is found to be A, then the relative abundances 25% and 75% respectively. Then the average atomic mass (in u) of element Z is:
A.66.6%
B.75%
C.25%
D.33.3%​

Answer 1

D) 33.3 %is that right

Answer 2

I think the question is wrong.

Or please correct your question