+0  
 
0
119
1
avatar+604 

Find the total number of four-digit palindromes. (Recall that a palindrome is a nonnegative sequence of digits which reads the same forwards and backwards, such as 1331. Zero cannot be the first digit.)

gueesstt  May 13, 2018
edited by Guest  May 13, 2018
 #1
avatar+945 
+2

There are two methods to do this problem.

 

Method 1: Pattern Finding

 

There are 9 palindromes with 2 digits 

There are 90 palindromes with 3 digits

There are 90 palindromes with 4 digits

 

Method 2: Counting

 

The 4 digit palindrome is in this format:

 

ABBA

 

There are 9 choices for A

10 for B

 

9*10=90

 

I hope this helped, 

 

Gavin

GYanggg  May 13, 2018

31 Online Users

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.