How Many Different Codes Can Be Generated
<p>To determine how many different four-digit capicúa (palindromic) numbers can be formed, we note that in a four-digit number, the first digit must be the same as the fourth, and the second must be the same as the third. Therefore, a four-digit capicúa number can be represented as:</p>
<p>ABBA</p>
<p>Where A and B are digits.</p>
<p>1. The first digit A can be any digit from 1 to 9 (9 options, since it can't be 0).</p>
<p>2. The second digit B can be any digit from 0 to 9 (10 options).</p>
<p>Thus, the total number of different capicúa numbers is given by:</p>
<p>Total = 9 \times 10 = 90</p>
