Theory:

A number comes before a number is called a predecessor and a number comes after a number is called a successor.
Rule for getting predecessor and successor:
  • Add \(1\) to a number to get the successor.
  • Subtract \(1\) to a number to get the predecessor.
Example:
1. Consider the number \(16\).
 
\(15\) comes before \(16\). So \(15\) is the predecessor of \(16\).
 
\(17\) comes after \(16\). So \(17\) is the successor of \(16\).
 
Verify: Add \(1\) to \(16\). \(16+1 =17\) - successor of \(16\).
 
Subtract \(1\) to \(16\). \(16-1=15\) - predecessor of \(16\).
 
 
2. Consider \(99999\).
 
\(99998\) comes before \(99999\). So \(99998\) is the predecessor of \(99999\).
 
\(100000\) comes after \(99999\). So \(100000\) is the successor of \(99999\).
 
 
3. Predecessor of smallest \(5\) digit number.
 
The smallest \(6\) digit number is \(10000\).
  
Subtract 1 to a number to get the predecessor.
 
Predecessor of \(10000 = 10000 - 1 = 9999\).