66.00
65.50
65.00
65.40
Correct answer is D
Isotope \(^{65}X_{30}\) (with a mass of 65 and an abundance of 60%):
Relative mass contribution = (65 * 60%) = 39.00
Isotope \(^{66}X_{30}\) (with a mass of 66 and an abundance of 40%):
Relative mass contribution = (66 * 40%) = 26.40
Now, add the relative mass contributions of both isotopes:
Relative atomic mass \(A_r\) = 39.00 + 26.40 = 65.40
So, the relative atomic mass of element X is 65.40. The correct option is:
65.40