Answer:
24.4 amu
Explanation:
1. Multiply the mass numbers by their percentages using the rules of significant figures:
Isotope 1: 24(.786) = 18.864 ⇒ 18.9
Isotope 2: 25(.101) = 2.525 ⇒ 2.53
Isotope 3: 26(.113) = 2.938 ⇒ 2.94
2. Find the sum of the products calculated using the rules of significant figures:
18.9 + 2.53 + 2.94 = 24.37 ⇒ 24.4
