Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 10 Counting Methods and Probability - 10.5 Find Probabilities of Independent and Dependent Events - 10.5 Exercises - Skill Practice - Page 722: 23



Work Step by Step

We know that $P(\text{A and B})=P(A)P(B|A)$, thus $P(B|A)=\frac{P(\text{A and B})}{P(A)}=\frac{\frac{1}{20}}{\frac{7}{20}}=\frac{1}{7}$
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