HW1_sol

# HW1_sol - CSE21 FA11 Homework#1 1.1 An n-digit number is a...

This preview shows pages 1–2. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CSE21 FA11 Homework #1 (9/26/11) 1.1. An n-digit number is a list of n digits where the first digit in the list is not zero (where we assume n ≥ 1). (a) How many n-digit numbers are there (as a function of n )? (b) How many n-digit numbers contain no 1’s? (c) How many n-digit numbers contain at least one 2? Solution: (a) There are 9 × 10 n- 1 n-digit numbers. (b) There are 8 × 9 n- 1 n-digit numbers. (c) Since there are 8 × 9 n- 1 n-digit numbers containing no 2’s, the number of n-digits containing at least one 2’s is 9 × 10 n- 1- 8 × 9 n- 1 . 1.2. In how many ways can a 10-person club select a president, a vice- president and a secretary-treasurer from among its members? What if the club has 6 men and 4 women and the three officers must consist of at least one man and at least one women? Solution: (a) The number of ways to select three officers in a 10-person club is 10 3 . (b) Since there are 6 3 ways to select three officers consisting of three men and there are 4 3 ways to select three officers consisting of three women, the number of ways to select three officers consisting of at least one man and at least one woman is 10 3- 6 3- 4 3 ....
View Full Document

## This note was uploaded on 02/02/2012 for the course CSE 21 taught by Professor Graham during the Fall '07 term at UCSD.

### Page1 / 3

HW1_sol - CSE21 FA11 Homework#1 1.1 An n-digit number is a...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online