Palindromic NumbersDate: 08/30/97 at 00:50:08 From: windows Subject: Palindromic numbers How many palindromic numbers are there between a) 10-100 b) 100-1000 c) 10-100000 ? Date: 09/03/97 at 10:47:03 From: Doctor Rob Subject: Re: Palindromic numbers a) Two-digit palindromes must have identical digits. You have 9 choices for the first digit (0 is excluded), and the second digit is determined for each, so the answer is 9. b) Three-digit palindromes must have identical first and last digits, but the middle digit is a free choice. There are 9 choices for the first digit (0 is excluded), and for each choice, there are 10 choices for the middle digit, so the answer is 9*10. c) 9 + 9*10 + 9*10 + 9*10^2 = 1089. Can you explain why? -Doctor Rob, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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