Use the formula for nCr to evaluate each expression. 4C4
Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations1h 43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 5m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
- Appendix 1. Review of Real Numbers2h 24m
- Appendix 2. Linear Equations and Inequalities3h 42m
- OLD 9. Sequences, Induction, and Probability Coming soon
- 1. - OLD - Fundamental Concepts of Algebra Coming soon
- 2. - OLD - Equations and Inequalities Coming soon
- OLD 4. Rational Functions Coming soon
- OLD 2. Functions & Graphs Coming soon
- OLD 6. Exponential and Logarithmic Functions Coming soon
- OLD 7. Systems of Equations and Inequalities Coming soon
- OLD 8. Matrices and Determinants Coming soon
- OLD 9. Conic Sections Coming soon
10. Combinatorics & Probability
Combinatorics
Multiple Choice
Phone numbers are 10 digits long. How many possible phone numbers are there if the 1st and 4th numbers can't be 0?
A
10
B
90
C
8,100,000,000
D
10,000,000,000
0 Comments
Verified step by step guidance1
Understand that a phone number is a sequence of 10 digits, where each digit can range from 0 to 9.
Identify the constraints: the 1st and 4th digits cannot be 0, meaning they can be any digit from 1 to 9.
Calculate the number of choices for the 1st digit: since it cannot be 0, there are 9 possible choices (1-9).
Calculate the number of choices for the 4th digit: similarly, there are 9 possible choices (1-9).
Calculate the number of choices for the remaining 8 digits: each can be any digit from 0 to 9, giving 10 choices per digit. Multiply the choices for each digit to find the total number of possible phone numbers.
Related Videos
Related Practice
Textbook Question

