#### Answer

85.47 u

#### Work Step by Step

Atomic mass of Rb = $(\frac{72.17}{100}\times84.912u)+(\frac{100-72.17}{100}\times86.909u)$= 85.47u.
Here, 100 is an exact number and it doesn't limit the number of significant figures.

Published by
Cengage Learning

ISBN 10:
0534420125

ISBN 13:
978-0-53442-012-3

85.47 u

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