4.5 x 10-4
An easy trick is to count the zeros.
The answer I believe would be A
Answer:
The answer to your question is: 85.458 amu
Explanation:
data
Rubidium-85 A = 84.9118 amu abundance = 72.15%
Rubidium - 87 A = 86.9092 amu abundance = 27.85%
Atomic weight = ?
Atomic weight = 84.9118(0.7215) + 86.9092(0.2785)
Atomic weight = 61.2538 + 24.2042
Atomic weight = 85.458 amu