Permutations-Combinations-and-Probability

A. For the Worksheet “Definitions and Word Problems-Part 1, Question 3 (Telephone numbers). I need an explanation of why the answer is 1/420. How do they get that.

B. For Test Form 1, I need explanations for the following problems:

Number 7-How did they get an answer of .79?

Number 8-How did they get an answer of 2/3? How do you solve this problem?

Number 10-How did they get an answer? Why is it correct?

Number 11-Why is a bar graph the correct answer?

Number 13-How do you solve this problem?

Number 14 How do you solve this problem?

Bonus-How do you solve this problem?

I think it will take far less than an hour to solve these problems.