Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 11 - Counting Methods and Probability Theory - 11.3 Combinations - Exercise Set 11.3 - Page 708: 47



Work Step by Step

The number of possible combinations if r items are taken from n items is nCr = $\frac{n!}{r!(n-r)!}$ The number of different ways four-letter passwords can be formed from the letters A, B, C, D, E, F, and G if no repetition of letters is allowed: = 7C4 x 4! =$\frac{7!}{4!(7-4)!}$ x 4! =7*6*5*4 = 840 ways
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.